Paediatric kidney clear cell sarcoma (often shortened to clear cell sarcoma of the kidney, CCSK) is a rare type of kidney cancer that happens mainly in young children, usually under 5 years of age. In this disease, cancer cells grow from the supporting (mesenchymal) tissue of the kidney, not from the normal filtering units. It is different from Wilms tumour, even though both are kidney cancers in children. CCSK makes up about 3–5% of all childhood kidney tumours and is known for its strong tendency to spread (metastasise), especially to bones and sometimes to the brain or lungs.
Paediatric kidney clear cell sarcoma (CCSK) is a rare, aggressive kidney cancer that almost always happens in young children, usually between 1 and 4 years of age. It grows from the supporting (mesenchymal) tissue of the kidney, not from the filtering units, and under a microscope the tumour cells often look pale or “clear.” Doctors used to call it the “bone-metastasizing renal tumour of childhood” because it can spread to bone and, more recently recognized, to the brain and lungs. [1]
Unlike the more common Wilms’ tumour, CCSK often has specific molecular changes such as internal tandem duplications in the BCOR gene, which help pathologists confirm the diagnosis. Children usually present with a large belly mass, abdominal pain, blood in the urine, or unexplained weight loss, and imaging (ultrasound, CT, MRI) followed by surgical removal and detailed pathology are needed to make the final diagnosis. [2]
The tumour often appears as a single large mass in one kidney. It usually has soft, pale, sometimes “clear-looking” cells when seen under the microscope, which is why it is called “clear cell” sarcoma. Children are often diagnosed around 3 years of age, and boys are affected slightly more often than girls.
Other Names
Clear cell sarcoma of the kidney has a few other names or phrases that doctors may use to describe the same condition:
Clear cell sarcoma of the kidney (CCSK) – the most common and correct medical name used today.
Renal clear cell sarcoma – “renal” means kidney, so this is another way to say the same tumour type.
Bone-metastasising renal tumour of childhood – an older name that was used because this tumour often spreads to bones more than other kidney cancers in children.
These different names can be confusing, but they all refer to the same paediatric kidney tumour.
Types
Doctors can describe paediatric kidney clear cell sarcoma in a few different “type” groups. These types are based on what the tumour looks like under the microscope, on genetic changes inside the cancer cells, and on how far the cancer has spread.
Classic clear cell sarcoma of the kidney – this is the most common microscopic pattern, with round to oval tumour cells arranged in nests and cords, often separated by delicate blood vessels.
Variant histologic patterns – some tumours show special patterns, such as myxoid (gel-like background), sclerosing (more fibrous tissue), epithelioid, spindle-cell, palisading, or anaplastic (very abnormal) changes. These patterns can make diagnosis more difficult, but they are still CCSK.
BCOR-ITD–positive CCSK – in most children, the tumour cells have an internal tandem duplication (ITD) in the BCOR gene. This is now considered the main molecular subtype and is very helpful for diagnosis.
YWHAE–NUTM2 fusion CCSK – a smaller group of tumours shows a different gene fusion between YWHAE and NUTM2. This is another recognised molecular type.
“Double-negative” CCSK – a rare group where the tumour does not show BCOR-ITD or YWHAE–NUTM2, but still has the typical CCSK look and behaviour.
Clinical stages (I–IV) – like many cancers, CCSK is staged according to how far it has spread: stage I is limited to the kidney; higher stages involve nearby tissues, lymph nodes, or distant organs such as bone, lung, or brain. Stage IV is the most advanced disease.
Causes
For most children with clear cell sarcoma of the kidney, doctors cannot find a single clear cause. The disease seems to arise from random genetic mistakes (mutations) in kidney cells as the child is developing. Many of the “causes” below are better thought of as contributing factors or scientific theories rather than proven triggers.
BCOR internal tandem duplication (BCOR-ITD)
In most CCSK tumours, the BCOR gene has a special type of mutation called an internal tandem duplication. This error changes how BCOR controls other genes and is thought to drive cancer growth. It is a “cause” at the cell level, but it does not explain why the mutation happened in that child.YWHAE–NUTM2 gene fusion
In a smaller number of children, CCSK cells show a fusion between the YWHAE and NUTM2 genes. This fusion joins parts of two different genes, creating an abnormal protein that may stimulate the tumour to grow and survive.Other BCOR gene rearrangements (such as BCOR–CCNB3)
Very rarely, clear cell sarcoma of the kidney carries a different BCOR-related fusion, such as BCOR–CCNB3, which is more typical in soft-tissue sarcomas. These abnormal gene joins change cell signalling and can act as another molecular cause in a small subgroup of patients.Errors during kidney development (embryonic origin)
CCSK appears to come from very early kidney precursor cells that did not mature properly during fetal development. When these primitive cells keep dividing instead of maturing, they may form a tumour later in early childhood.Random (sporadic) DNA mutations
Most children with CCSK do not have a family history of kidney cancer or known inherited syndromes. This suggests that many cases result from random spontaneous mutations in kidney cells that happen by chance and are not passed down from parents.Male sex
CCSK is reported more often in boys than in girls, with roughly a 2:1 ratio. Being male does not “cause” the tumour directly, but it is a known risk pattern and may reflect underlying biological differences such as hormones or gene activity.Young age (early childhood)
Most cases are diagnosed in children under 4 years of age. This early age pattern supports the idea that CCSK begins from abnormal development processes in the kidney rather than from long-term environmental exposures.Lack of association with common cancer syndromes
Unlike Wilms tumour, CCSK is generally not linked to well-known genetic syndromes (such as WAGR or Beckwith–Wiedemann). This absence suggests that its causes lie in a different set of genetic changes that occur only in the tumour, not throughout the child’s body.General childhood cancer susceptibility genes (theoretical)
Some children may have subtle inherited variations in genes that repair DNA or control cell growth. These do not cause CCSK on their own but may make it easier for BCOR-related mutations or other errors to lead to cancer if they occur. Evidence here is still limited and under study.Parental age (possible influence)
Studies in childhood renal tumours as a group suggest that older maternal or paternal age might slightly increase the risk of kidney cancers in children. This has not been proven specifically for CCSK, but it is considered as a broader risk factor for paediatric renal tumours.Perinatal environmental exposures (extrapolated from Wilms tumour)
For some childhood kidney cancers, research suggests that exposure to pesticides during pregnancy may increase risk. While data focus mostly on Wilms tumour, similar mechanisms could potentially influence CCSK, but this has not been clearly confirmed.Maternal smoking (possible weak risk)
Maternal smoking during pregnancy is a suspected risk for several childhood cancers. It may increase DNA damage or reduce oxygen supply to the developing fetus. Direct proof in CCSK is lacking, but it remains a general concern for paediatric tumours.Household pesticide use in pregnancy (theory)
Some studies show that frequent use of insecticides in the home during pregnancy is linked to higher risk of childhood kidney cancers in general. If similar mechanisms apply, such chemicals might contribute to the mutations seen in CCSK in a small number of cases.Abnormal growth patterns at birth (birthweight, prematurity – extrapolated)
High or very low birthweight, prematurity, or growth restriction have been associated with some paediatric tumours. They may indicate stress or abnormal growth signals during fetal life, which could make kidney precursor cells more vulnerable to turning cancerous.Radiation exposure (very rare in children)
Radiation is a known cause of many cancers, but children rarely receive high doses to the kidneys. Prior therapeutic radiation to the abdomen could, in theory, raise the risk of a second cancer like CCSK years later, though this is extremely rare and not clearly documented.Previous chemotherapy (for another cancer)
Some chemotherapies can damage DNA and rarely cause second cancers after treatment. While most CCSK cases are primary tumours, prior chemotherapy could theoretically contribute in children who already had another cancer, although this is not a typical pattern.Immune dysregulation (general cancer risk idea)
Weak or poorly functioning immune systems can make it harder to detect and remove abnormal cells. This is a recognised concept in cancer biology, but there is no strong direct link yet proven between immune disorders and CCSK specifically.Epigenetic changes (changes in gene “on–off” signals)
CCSK shows patterns of gene expression and chromatin modification that differ from normal kidney tissue. These epigenetic changes can silence protective genes or activate growth pathways, helping to maintain the tumour once it has formed.Activation of pathways like Sonic Hedgehog and Akt
Research has shown that CCSK cells often activate specific signalling pathways, such as Sonic Hedgehog and Akt, which tell cells to keep dividing and avoid cell death. Activation of these pathways is thought to be part of the mechanism that drives growth and survival of the tumour.Currently unknown or multifactorial causes
For most individual children, the real cause of CCSK is unknown. It is likely that a mix of random genetic errors, individual biology, and perhaps small environmental influences all come together to start the cancer. Ongoing research aims to clarify these complex interactions.
Symptoms
Palpable abdominal mass or swelling
The most common sign is a lump or swelling in the child’s tummy that parents may notice while bathing or dressing the child. This mass is usually painless at first and may grow slowly, making one side of the abdomen look larger or more firm.Abdominal pain or discomfort
As the tumour grows, it can stretch the kidney capsule or press on nearby organs, causing dull or aching pain in the abdomen or flank. Small children may just become irritable or cry more, while older children can point to the painful area.Visible blood in the urine (gross hematuria)
Some children pass urine that looks pink, red, or tea-coloured because of blood coming from the affected kidney. This can happen off and on and may be painless. Any visible blood in a child’s urine needs urgent medical review.Microscopic blood in the urine
In many cases, blood is present in the urine but not visible to the eye. It is only picked up by a urine test. This silent bleeding happens because fragile tumour blood vessels break easily.High blood pressure (hypertension)
The tumour can affect blood flow in the kidney or disrupt hormones that control blood pressure, leading to hypertension. Parents may notice headaches, nosebleeds, or dizziness, but often high blood pressure is found during clinic checks.Fever without clear infection
Some children have repeated fevers even when there is no obvious infection. This can be due to inflammatory chemicals released by the tumour or minor bleeding inside the mass.Vomiting and nausea
A large tumour may press on the stomach or intestines, causing nausea and vomiting. These symptoms can be mistaken for common stomach bugs at first, which sometimes delays diagnosis.Constipation or change in bowel habits
The mass can compress the intestines and slow movement of stool. Children may have constipation, less frequent bowel movements, or abdominal bloating, which may be noticed over weeks.Loss of appetite (poor feeding)
Many children with CCSK eat less and feel full quickly because of stomach pressure or general illness. Parents may notice that the child refuses feeds, snacks less, or loses interest in favourite foods.Weight loss or poor weight gain
Over time, reduced appetite and the energy demands of the tumour lead to weight loss or failure to gain weight as expected. Clothes may become loose, and growth charts may show flattening or dropping centile lines.Pallor and tiredness (from anaemia)
Children can become pale, tired, and less active if they have anaemia. Anaemia may result from chronic blood loss in the urine or from the cancer affecting bone marrow function or general health.Back pain or flank pain
The tumour can stretch tissues around the kidney or press backwards, causing pain felt in the back or side (flank). Older children may complain of back ache, especially when running, jumping, or lying on one side.Bone pain or limping (from bone metastases)
CCSK has a strong tendency to spread to bones. When this happens, children may develop persistent bone pain, refusal to walk, limping, or even fractures after minor falls. Bone pain that does not go away needs urgent assessment.Headaches, vomiting, or seizures (from brain involvement)
If the cancer spreads to the brain, children can develop severe headaches, vomiting, changes in behaviour, weakness of limbs, or seizures. Brain spread is less common at first diagnosis but can occur, especially at relapse.Breathing problems or cough (from lung or chest spread)
Metastases in the lungs or chest may cause cough, shortness of breath, chest pain, or recurrent chest infections. These symptoms usually appear in more advanced disease and always require rapid medical evaluation.
Diagnostic Tests
Doctors use a combination of clinical examination, manual bedside tests, laboratory and pathology studies, electrodiagnostic tests, and imaging to diagnose paediatric kidney clear cell sarcoma and to plan treatment. No single test is enough by itself; all the results are put together to make the final diagnosis.
Physical Exam Tests
General paediatric physical examination and vital signs
The doctor first checks the child’s overall condition: heart rate, breathing rate, temperature, and oxygen levels. They look for signs of illness such as pallor, tiredness, fever, or breathing difficulty. This broad examination helps to judge how sick the child is and guides which urgent tests are needed.Focused abdominal observation and auscultation
The abdomen is carefully looked at for visible swelling, bulging on one side, or stretched veins. The doctor listens with a stethoscope for bowel sounds. A large kidney tumour can push the belly wall forward and change the normal outline of the tummy.Growth and nutritional assessment
The child’s weight, height, and head size (in younger children) are measured and plotted on growth charts. Poor weight gain, weight loss, or stunted growth can indicate long-standing disease or nutritional stress due to cancer.
Manual Tests
Abdominal palpation for a kidney mass
Using gentle hand pressure, the doctor feels the child’s abdomen to detect any lump or firm area. In CCSK, the tumour often feels like a large, firm, smooth mass on one side. This simple manual test is often the first step that raises suspicion of a kidney tumour.Abdominal percussion to map organ borders
The doctor taps on the abdomen with their fingers and listens to the sound. Solid organs and tumours sound more “dull” than air-filled bowel. Percussion helps to estimate the size and location of the mass and to distinguish it from gas-filled intestines.Manual blood pressure measurement
Blood pressure is checked with an appropriately sized cuff. High blood pressure is common in childhood renal tumours and can be a clue that the kidney is involved. Regular measurements also help to monitor the child’s response to treatment.Musculoskeletal examination for bone tenderness or limping
The doctor gently presses along the bones and joints and watches the child walk or stand. Areas of tenderness, refusal to bear weight, or limping can suggest bone metastases, which are more common in CCSK than in many other kidney tumours.
Lab and Pathological Tests
Complete blood count (CBC)
A CBC measures red cells, white cells, and platelets. Children with CCSK may have anaemia from chronic blood loss or illness, and sometimes changes in white cells or platelets. The CBC also provides a baseline before chemotherapy, which can affect blood counts.Kidney function tests (serum creatinine and urea/BUN)
These blood tests show how well the kidneys are working. Even though only one kidney is usually affected, a very large tumour or treatment can reduce kidney function. Doctors need these results before surgery and chemotherapy to plan safe doses.Liver function tests and LDH (lactate dehydrogenase)
Liver enzymes, bilirubin, and LDH are checked to look for general illness, liver involvement, or tumour activity. LDH can be raised in many aggressive cancers and may reflect the burden of disease, although it is not specific to CCSK.Urinalysis and urine microscopy
A simple urine dipstick test can detect blood and protein in the urine. Microscopy can confirm red blood cells and look for other abnormalities. This test is quick and non-invasive and often shows microscopic blood even when urine looks normal.Coagulation profile (clotting tests)
Tests such as PT, aPTT, and fibrinogen measure the blood’s ability to clot. They are important before surgery and in seriously ill children, because some cancers and treatments can disturb clotting and increase bleeding risk.Histopathologic examination of the kidney tumour
After the kidney and tumour are removed (or after a biopsy in selected cases), a pathologist studies thin slices of tissue under the microscope. In CCSK, they see characteristic clear or pale cells with a specific pattern of growth, which distinguishes it from Wilms tumour and other masses. Histology is essential for the final diagnosis.Immunohistochemistry (IHC) panel
IHC uses antibodies to stain for certain proteins. CCSK usually shows strong BCOR and cyclin D1 staining and is negative for typical Wilms tumour markers. This staining pattern helps confirm CCSK, especially in difficult cases or unusual histologic types.Molecular genetic testing for BCOR-ITD and YWHAE–NUTM2
Special molecular tests (such as PCR or sequencing) can detect BCOR internal tandem duplication or YWHAE–NUTM2 fusions in the tumour tissue. Finding these changes strongly supports the diagnosis of CCSK and may help classify the tumour into a specific subtype.
Electrodiagnostic Tests
Electrocardiogram (ECG)
An ECG records the electrical activity of the heart. It is usually normal in CCSK itself, but it is very important before and during treatment because some chemotherapy drugs (such as anthracyclines) can affect the heart. ECG helps to ensure the child’s heart is safe to receive these medicines.Echocardiogram (cardiac ultrasound)
An echocardiogram uses ultrasound to take moving pictures of the heart. It checks how well the heart muscle pumps blood and whether there is any damage from treatment. This test is often done before, during, and after chemotherapy in children with CCSK.Electroencephalogram (EEG) for neurological symptoms
If the child has seizures or other signs that suggest brain involvement, an EEG may be used to measure brain electrical activity. While imaging is more important for detecting brain metastases, EEG can help characterise seizure patterns and guide neurological care.
Imaging Tests
Abdominal ultrasound
Ultrasound is usually the first imaging test used when a mass is suspected. It is quick, painless, and does not use radiation. The scan can show a solid kidney tumour, its size, and whether it is likely to be arising from the kidney rather than the liver or other organs.Contrast-enhanced CT and/or MRI of the abdomen and chest
CT or MRI scans with contrast give detailed cross-sectional images of the kidney, tumour, nearby organs, lymph nodes, lungs, and bones. They help to stage the tumour, plan surgery, and look for spread to distant sites. CT is often used for the chest to check for lung metastases, while MRI can be helpful for detailed soft-tissue and bone assessment.
Non-pharmacological treatments (therapies and other supports)
Below are key non-drug therapies commonly used around the world in children with CCSK. They do not replace chemotherapy or surgery; they support the child and family and help manage side-effects. Always discuss any therapy with the paediatric oncology team.
Multidisciplinary paediatric oncology team care
Care in a children’s cancer centre brings together paediatric oncologists, surgeons, radiation oncologists, specialist nurses, dietitians, physiotherapists, psychologists and social workers. Working as a team improves staging accuracy, treatment planning, side-effect management and long-term follow-up, and is strongly linked with better survival in childhood cancers. [4]Nutrition therapy and dietitian support
Good nutrition helps children tolerate chemotherapy, recover from surgery and maintain growth. Paediatric oncology dietitians assess weight, growth charts and lab tests, then design high-calorie, high-protein meal plans, use oral supplements and, when needed, tube feeding or IV nutrition. These steps can reduce treatment interruptions, speed wound healing and improve overall quality of life. [5]Physical therapy and gentle exercise programmes
Physiotherapists create simple activity plans (stretching, walking, play-based exercises) that match the child’s energy level and blood counts. Regular, safe movement helps maintain muscle strength, reduce fatigue, protect bones and joints, and improve mood, without increasing relapse risk when done carefully under medical advice. [6]Psychological counselling and play therapy
Clinical psychologists and child-life specialists use age-appropriate play, stories, drawing and simple conversations to help children cope with fear, procedures and hospital stays. For parents, counselling provides tools to manage anxiety, insomnia and decision stress, which in turn supports better care for the child. [7]Educational and school-reintegration support
Teachers linked to the hospital or home-schooling programmes keep children engaged with learning during treatment. Staying connected to schoolwork and classmates supports emotional health and reduces the shock of returning to school after months of therapy. [8]Infection-prevention training for families
Nurses teach families about handwashing, mask use when needed, safe food handling, avoiding sick contacts and what to do when a fever appears. These non-drug measures are critical because chemotherapy weakens immunity and infections can become life-threatening very quickly in neutropenic children. [9]Oral care and mucositis prevention routines
Daily soft-bristle brushing, bland mouth rinses and careful monitoring of the mouth reduce painful sores (mucositis) caused by chemo. Good oral hygiene lowers infection risk, helps children eat better and may reduce the need for IV pain medicines. [10]Sleep and daily-routine support
Maintaining a predictable routine (regular bedtime, quiet time before sleep, limited nighttime vital-sign checks when safe) can reduce anxiety and fatigue. Better sleep has been linked with improved mood, concentration and coping in children with cancer. [11]Rehabilitation and long-term survivorship clinics
After treatment, survivorship programmes monitor growth, heart and kidney function, learning, fertility and mental health. Early detection of late effects from chemotherapy or radiotherapy allows timely interventions, such as cardiac medicines, hormone replacement or neurocognitive support. [12]Integrative therapies (music, art, relaxation) under supervision
Music therapy, art therapy, simple breathing exercises and mindfulness can reduce perceived pain and procedure-related stress. These should always be coordinated with the oncology team to avoid conflicts with medical procedures and to ensure safety. [13]
Drug treatments
Chemotherapy for paediatric kidney clear cell sarcoma almost always uses combinations of several drugs. The exact plan (names, doses, number of cycles) depends on stage, spread and national protocol. Below are important FDA-approved medicines used in CCSK regimens or as essential supportive drugs; prescribing details come from their official labels and major paediatric renal tumour studies. Always remember: dosing is individualized by paediatric oncologists using body-surface area and organ function tests.
Vincristine sulfate – Vinca alkaloid chemotherapy
Vincristine blocks microtubule formation, stopping rapidly dividing cancer cells from separating their chromosomes, which leads to cell death. It is usually given once weekly by IV and is a backbone drug in CCSK regimens like vincristine/doxorubicin/cyclophosphamide with etoposide and carboplatin. Typical dosing is calculated in mg/m², with strict maximum single doses, and main side-effects include nerve damage (tingling, foot drop), constipation and low blood counts. [14]Doxorubicin hydrochloride – anthracycline chemotherapy
Doxorubicin intercalates into DNA and inhibits topoisomerase II, causing breaks that cancer cells cannot repair. It is commonly added to vincristine-based regimens for CCSK because studies showed better relapse-free survival when doxorubicin was included. Doses are given IV over minutes to hours and limited by lifetime cumulative exposure due to possible heart muscle damage; other side-effects include hair loss, mouth sores, nausea and severe lowering of blood counts. [15]Cyclophosphamide – alkylating agent
Cyclophosphamide attaches alkyl groups to DNA, interfering with replication in tumour cells. In paediatric protocols it is used in combination blocks (for example with vincristine and doxorubicin) and dosing is based on body-surface area or weight, adjusted for kidney function and prior toxicity. Key side-effects are bone-marrow suppression, hair loss, nausea, fertility impact and a risk of bladder irritation or bleeding, so vigorous hydration and sometimes MESNA are used for protection. [16]Dactinomycin (Cosmegen) – actinomycin D
Dactinomycin binds tightly to DNA and blocks RNA synthesis, which slows cell division and triggers cell death. It has long been part of Wilms’ tumour therapy and is also used in some CCSK regimens. It is given by IV push or short infusion with dosing based on body-surface area, and can cause severe bone-marrow suppression, mouth sores, liver toxicity, nausea and an increased risk of serious tissue damage if it leaks outside the vein. [17]Etoposide / etoposide phosphate – topoisomerase II inhibitor
Etoposide blocks the enzyme topoisomerase II, causing double-strand DNA breaks in dividing cells. Regimens for higher-stage or relapsed CCSK frequently combine etoposide with carboplatin or ifosfamide to improve control of metastatic disease, especially in bone or brain. It is given IV over 30–60 minutes for several days per cycle, and main toxicities include low blood counts, hair loss, nausea and a small long-term risk of secondary leukaemia. [18]Carboplatin – platinum chemotherapy
Carboplatin forms DNA cross-links that prevent cancer cells from copying their genetic material. In advanced CCSK, carboplatin-containing regimens have shown benefit, particularly for stage IV disease with distant spread. Dosing is often calculated using a formula based on kidney function (glomerular filtration rate and target area under the curve), and principal side-effects are low platelets and white cells, nausea, vomiting and, less commonly, kidney or hearing problems. [19]Ifosfamide – alkylating agent used in relapse or high-risk disease
Ifosfamide is related to cyclophosphamide and also cross-links DNA. It is widely used in relapse protocols like ICE (ifosfamide, carboplatin, etoposide) for metastatic CCSK, and must always be given with strong hydration and MESNA to protect the bladder. Typical courses last several consecutive days by IV infusion, and side-effects include bone-marrow suppression, kidney and bladder toxicity, confusion or sleepiness (encephalopathy) and nausea. [20]MESNA (mesnex) – uroprotective agent
MESNA is not an anticancer drug, but it binds and neutralizes toxic breakdown products of ifosfamide and high-dose cyclophosphamide in the urine. It is given IV or orally in timed doses around the chemotherapy administration, greatly reducing the risk of haemorrhagic cystitis (bleeding and inflammation of the bladder). Side-effects are usually mild, such as nausea, vomiting or headache, and its use is standard whenever ifosfamide is used. [21]Filgrastim (Neupogen) – G-CSF to boost white cells
Filgrastim is a recombinant granulocyte colony-stimulating factor (G-CSF) that signals the bone marrow to make more neutrophils. In CCSK protocols it is given as short daily injections under the skin after chemotherapy cycles to shorten the period of severe neutropenia, lower rates of febrile neutropenia and help keep treatment on schedule. Common side-effects are bone pain, injection-site redness and rarely spleen enlargement or lung problems, so children are monitored closely. [22]Pegfilgrastim (Neulasta and biosimilars) – long-acting G-CSF
Pegfilgrastim is a pegylated (long-acting) form of G-CSF given as a single injection once per chemotherapy cycle instead of daily filgrastim. It provides prolonged stimulation of neutrophil production and is widely used with myelosuppressive regimens in solid tumours and sarcomas to reduce infection risk. Side-effects are similar to filgrastim, and dosing in children is weight-based with careful timing relative to chemo. [23]
Very important: Drug names and general mechanisms are educational only. Doses, schedules and combinations for a child must always be decided by a paediatric oncologist using official protocols and FDA labels. Never try to obtain or use these medicines without a hospital team.
Dietary molecular supplements (supportive, not curative)
Dietary supplements should never replace standard cancer treatment and can sometimes interact with chemotherapy. All supplements must be approved by the oncology team and paediatric dietitian.
Standard paediatric multivitamin (no high-dose antioxidants)
A regular-dose multivitamin may be used when blood tests show mild deficiencies or intake is poor. It helps cover basic needs for vitamins A, B complex, C and D and some minerals, but doses are kept within normal dietary ranges to avoid interfering with chemotherapy effects. [24]Vitamin D (cholecalciferol) when deficient
Many children with cancer have low vitamin D levels, which can affect bones, muscles and immunity. If tests confirm deficiency, doctors may prescribe a daily or weekly oral dose suited to age and level; this supports bone health, especially when steroids, reduced mobility or kidney issues are present. [25]Calcium supplementation in selected cases
When dietary intake is poor or steroids and limited activity weaken bones, calcium supplements might be used along with vitamin D. The dose is adjusted so that total calcium (diet + supplement) stays within safe limits, to support bone mineralisation without causing kidney stones, especially in children with a single kidney. [26]Iron supplements only for proven iron-deficiency anaemia
Chemotherapy often causes anaemia, but iron tablets are only helpful if blood tests show low iron stores. In that case, doctors may prescribe weight-based iron doses to rebuild stores and support energy and growth; if anaemia is due mainly to chemo or chronic disease, transfusions rather than iron may be preferred. [27]Folate and vitamin B12 for documented deficiency
Folate and B12 are needed for red blood cell production. If tests show deficiency, carefully dosed supplements can correct macrocytic anaemia and support recovery. However, high doses without a proven deficiency are avoided because they may theoretically affect cancer-cell growth. [28]Omega-3 fatty acids (fish-oil-based) under guidance
Omega-3 fatty acids from fish oil or algae are being studied for effects on inflammation, weight maintenance and mood in paediatric oncology. Low-to-moderate doses may help some children with appetite or weight stabilisation, but they can slightly increase bleeding risk, so they should be used only with oncologist approval and stopped before surgeries. [29]High-energy oral nutrition supplements (e.g., protein drinks)
Commercial high-calorie, high-protein drinks are often considered “medical foods” rather than classic supplements but are very important in practice. They provide concentrated calories, proteins and micronutrients in small volumes for children who tire quickly when eating; dietitians choose specific products and volumes based on age and tolerance. [30]Probiotics – only in very carefully selected cases
Some data in general paediatrics suggest selected probiotic strains may help bowel function, but in children with severe neutropenia, there is a small risk of bloodstream infection from probiotic organisms. For this reason, many paediatric oncology guidelines either avoid probiotics during intensive chemo or use them only within research protocols. [31]Zinc supplementation when low
Zinc plays a role in immunity, taste and wound healing. If blood levels or clinical signs suggest deficiency (poor growth, repeated infections, taste changes), doctors may prescribe a short course of zinc; doses are kept within paediatric reference ranges to avoid nausea or copper deficiency. [32]Electrolyte and trace-element supplementation via feeds or IV
In children who need tube feeding or parenteral nutrition, the “supplements” are balanced inside the formula: potassium, magnesium, phosphate and trace elements. These are tightly adjusted based on frequent blood tests to support heart rhythm, nerve function and metabolism during chemo. [33]
Immunity-booster, regenerative and stem-cell-related drugs
These medicines are used by hospital teams to support immunity and marrow recovery; they are not over-the-counter products.
Filgrastim (G-CSF) for neutrophil recovery
As described above, filgrastim stimulates neutrophil production in the marrow, shortens neutropenia and lowers infection risk, acting as a powerful “immunity booster” in a controlled hospital setting. It is given by daily injections after chemotherapy until white cell counts recover, with careful monitoring for bone pain, spleen enlargement and rare lung complications. [34]Pegfilgrastim (long-acting G-CSF)
Single-dose pegfilgrastim per cycle maintains raised neutrophil levels for longer, reducing the burden of daily injections while providing similar protection against febrile neutropenia. It is timed carefully (usually at least 24 hours after chemo) to avoid overlapping with cytotoxic drug action. [35]Granix (tbo-filgrastim) and other G-CSF biosimilars
Biosimilar G-CSFs such as tbo-filgrastim provide similar biological effects to originator filgrastim with strict regulatory requirements for safety and efficacy. They are increasingly used worldwide to support white blood cell recovery and maintain access to growth-factor therapy in resource-limited settings. [36]Intravenous immunoglobulin (IVIG) in selected immune deficits
IVIG contains pooled antibodies from healthy donors and may be used if children with CCSK develop significant antibody deficiency or specific immune problems during long-term treatment. It is infused in hospital over hours, can reduce serious infections in certain immune defects and may cause side-effects such as headache, fever or rare allergic reactions. [37]Haematopoietic stem cell transplantation (HSCT)
For very high-risk or relapsed CCSK, some centres consider high-dose chemotherapy followed by reinfusion of previously collected stem cells (autologous HSCT). This “resets” the bone marrow after very intensive chemo but carries serious risks such as infections, organ damage and long hospital stays, so it is reserved for carefully selected cases or clinical trials. [38]Experimental cellular therapies in clinical trials
In the future, immunotherapies like CAR-T cells or engineered NK cells may be tested for rare paediatric solid tumours. At present, these approaches are experimental for CCSK and only available inside tightly controlled clinical studies. Families interested in research options should talk with their paediatric oncologist about registries and trial centres. [39]
Surgeries for paediatric kidney clear cell sarcoma
Radical nephrectomy with lymph-node sampling
The main operation for CCSK is radical nephrectomy: removing the entire affected kidney, nearby fatty tissue and regional lymph nodes through an abdominal incision. This allows full tumour removal when possible, accurate staging and tissue for diagnosis, and is usually the first big step in cure. [40]Nephron-sparing surgery in selected cases
In rare situations (for example, a small tumour in one kidney and problems with the other kidney), surgeons may remove only the tumour and a rim of normal tissue, preserving more kidney units. This is technically difficult in CCSK and is used only in specialised centres when the benefits clearly outweigh the risks of leaving tumour behind. [41]Resection of metastatic lesions (lung, bone, soft tissue)
If CCSK has spread but shows a good response to chemotherapy, surgeons may remove remaining lung nodules or bone/soft-tissue metastases. Taking out these “residual” lesions can improve local control and, combined with systemic therapy, may increase the chance of long-term survival in selected children. [42]Neurosurgery for brain metastases
CCSK can rarely spread to the brain. When a brain mass causes symptoms (headache, seizures, weakness) and is operable, neurosurgeons may remove it to relieve pressure and obtain tissue, followed by radiotherapy and systemic chemo. This is complex, high-risk surgery that requires a paediatric neurosurgical team. [43]Central venous access device placement (port or Hickman line)
Long-term chemotherapy, blood draws and transfusions are much easier and safer with a surgically placed central line or implanted port. This short procedure under general anaesthesia reduces repeated needle sticks and allows reliable delivery of vesicant drugs like doxorubicin and dactinomycin. [44]
Preventions and risk-reduction
At present, there is no known way to prevent CCSK from developing, because its exact causes are not fully understood and it is not linked to lifestyle or parenting. Prevention focuses on reducing complications and long-term health risks:
Prompt evaluation of any persistent abdominal mass, swelling or blood in the urine in a child. [45]
Early referral to a paediatric cancer centre if a renal tumour is suspected. [46]
Strict adherence to chemotherapy and follow-up schedules to reduce relapse risk. [47]
Careful infection-prevention at home (handwashing, avoiding sick contacts) during neutropenia. [48]
Balanced, high-nutrient diet with dietitian support to avoid under- or over-nutrition. [49]
Appropriate vaccinations and revaccination plans after treatment as advised by the oncology team. [50]
Regular monitoring of heart, kidney and growth parameters to catch late effects early. [51]
Avoiding tobacco smoke exposure at home, which can worsen overall health and lung function. [52]
Encouraging age-appropriate physical activity to support cardiovascular and bone health. [53]
Lifelong survivorship follow-up in a late-effects clinic when available. [54]
When to see doctors
A child should be seen urgently by a doctor, and usually by a paediatric oncologist, if any of these happen:
A firm or growing lump/swelling in the abdomen, especially if one side seems bigger.
Blood in the urine, persistent flank or abdominal pain, or suddenly enlarged belly.
Unexplained fever, weight loss, tiredness or pallor lasting more than a couple of weeks.
During treatment: any fever ≥38 °C, shaking chills, difficulty breathing, severe vomiting/diarrhoea, very reduced urine output, sudden headaches, seizures, bone pain or new neurological symptoms.
These signs do not always mean cancer or relapse, but in a child with known CCSK or a single kidney they are emergencies and must be checked immediately. [55]
What to eat and what to avoid
Food choices must be individualised by the oncology team and dietitian, especially when blood counts are low or the remaining kidney is under stress. General principles often used in paediatric oncology nutrition are:
Helpful to eat (as tolerated):
Small, frequent meals rich in calories and protein: eggs, lentils, lean meats, fish, cheese, nut butters (if safe for age and allergies).
Soft, easy-to-swallow foods when mouth sores or nausea are present, such as soups, yoghurt, smoothies and mashed vegetables.
Well-washed fruits and cooked vegetables to provide vitamins and fibre, avoiding raw produce if severely neutropenic as per local policy.
Healthy fats like olive oil and avocado to increase calories in small portions.
Plenty of safe fluids (water, oral rehydration solutions) to protect the remaining kidney, adjusted by the medical team.
Usually avoided or restricted:
Raw or undercooked meat, eggs, seafood and unpasteurised milk or juices, which can carry dangerous germs.
Buffet, street or leftover foods stored incorrectly, especially during neutropenia.
Very salty, heavily processed snacks that can strain blood pressure and the single kidney.
High-dose herbal or antioxidant supplements (pills, mega-dose vitamins) without oncologist approval because they may interact with chemo.
Sugary drinks and sweets in large amounts, which add calories but few nutrients and may worsen weight or blood sugar control.
These recommendations are adapted from paediatric oncology nutrition guidelines and should always be personalised. [56]
Frequently asked questions (FAQs)
Is paediatric clear cell sarcoma of the kidney curable?
Yes, many children with CCSK can be cured, especially when the tumour is found early and treated in a specialised paediatric cancer centre with surgery and combination chemotherapy. Survival is highest in stage I–II disease, but even advanced cases can achieve long remissions with modern regimens. [57]How is CCSK different from Wilms’ tumour?
Both are kidney cancers in children, but CCSK arises from different cells, looks different under the microscope, has unique BCOR-related molecular changes and has a higher tendency to spread to bone and brain. Because of this, it usually needs more intensive and longer chemotherapy than most Wilms’ tumours. [58]What causes CCSK? Did parents do something wrong?
Current evidence suggests that CCSK results from genetic and developmental changes in kidney tissue during early life, not from anything parents did or did not do. There are no clear links with diet, environmental exposures or infections in most children. [59]Will my child live a normal life with one kidney?
Many children live full, active lives with a single kidney, especially when blood pressure and kidney function are checked regularly and healthy lifestyle habits are followed. Long-term follow-up is still vital to catch any later kidney or blood-pressure problems early. [60]Why is chemotherapy necessary after the tumour is removed?
Even after a complete nephrectomy, tiny groups of cancer cells may remain in the body. Chemotherapy circulates through the bloodstream to kill these invisible cells and reduce the risk of relapse in distant sites like bone or brain. [61]Is radiotherapy always used?
No. Radiotherapy decisions depend on stage, surgical margins and protocol. Some stage I children with completely removed tumours may avoid radiotherapy, while others with higher-stage or residual disease may receive targeted flank or brain radiotherapy to reduce relapse risk. [62]Can CCSK come back after treatment?
Relapse is possible, often in the brain, lungs or bone, especially in higher-stage disease. Intensive salvage therapy using combinations like ifosfamide, carboplatin and etoposide, sometimes with radiotherapy and stem-cell transplant, can still achieve second remissions in some children. [63]How often will my child need scans?
Follow-up schedules differ, but typically involve more frequent imaging (ultrasound, chest X-ray or CT/MRI) and lab tests during the first few years after treatment, when relapse risk is highest, then less frequently in long-term survivorship. Your team will provide a written plan. [64]Can my child have vaccines during or after chemo?
Inactivated (killed) vaccines may be given in some phases, but live vaccines are usually delayed until the immune system has recovered. After treatment, many children need to repeat or boost some vaccinations; this is planned with the oncology and primary-care teams. [65]Are alternative or herbal treatments safe?
Many herbal products and “natural” supplements may interact with chemotherapy or affect blood clotting, liver or kidney function. Because quality and contents can vary, paediatric oncologists usually advise against unproven alternative treatments and favour evidence-based supportive care instead. [66]Can we use special anti-cancer diets from the internet?
Strict or extreme diets (very low-carb, raw-only, juice-only) can lead to dangerous weight loss and nutrient deficiencies in children already under treatment stress. Evidence supports balanced, flexible diets tailored by a paediatric oncology dietitian rather than restrictive “cancer cure” diets. [67]What long-term side-effects should we watch for?
Possible late effects include reduced kidney function, high blood pressure, growth or puberty problems, learning or attention difficulties, heart weakness from anthracyclines and second cancers in rare cases. Regular survivorship clinic visits help detect and manage these early. [68]Can my child play sports during treatment?
Light activity and play are usually encouraged when blood counts and energy are adequate, but contact sports and activities with high fall risk are often restricted during periods of low platelets or severe anaemia. The oncology and physiotherapy teams help design safe activity plans. [69]Should brothers and sisters be screened?
CCSK is usually not inherited, and routine screening of siblings is not recommended unless a specific genetic syndrome is identified by a clinical geneticist. However, families should inform doctors about any strong family history of childhood cancers or kidney problems. [70]Where can families find support?
Families can get help from hospital social workers, national childhood cancer foundations, parent-to-parent support groups and survivorship programmes. These groups offer emotional support, financial guidance and reliable education materials written for parents and teenagers. [71]
Disclaimer: Each person’s journey is unique, treatment plan, life style, food habit, hormonal condition, immune system, chronic disease condition, geological location, weather and previous medical history is also unique. So always seek the best advice from a qualified medical professional or health care provider before trying any treatments to ensure to find out the best plan for you. This guide is for general information and educational purposes only. Regular check-ups and awareness can help to manage and prevent complications associated with these diseases conditions. If you or someone are suffering from this disease condition bookmark this website or share with someone who might find it useful! Boost your knowledge and stay ahead in your health journey. We always try to ensure that the content is regularly updated to reflect the latest medical research and treatment options. Thank you for giving your valuable time to read the article.
The article is written by Team RxHarun and reviewed by the Rx Editorial Board Members
Last Updated: January 28, 2025.
