Mucinous tubular and spindle cell carcinoma (MTSCC) of the kidney is a rare subtype of renal cell carcinoma (RCC), accounting for less than 1% of all kidney cancers. It was first recognized as a distinct entity in the 2004 World Health Organization classification and is characterized by its unique mixture of tubular structures, spindle cell components, and variable extracellular mucinous stroma WikipediaBioMed Central. Although generally considered a low‑grade, indolent tumor with favorable outcomes, occasional cases exhibit high‑grade features and aggressive behavior PMCPMC.
MTSCC is a rare, low‑grade subtype of renal cell carcinoma, accounting for less than 1% of all kidney cancers. It predominantly affects middle‑aged women and is characterized histologically by elongated tubules and spindle‑shaped tumor cells embedded in a mucinous stroma autopsyandcasereports.orgturkjpath.org. Clinically, patients often present incidentally on imaging, though some may experience hematuria or flank pain. Prognosis is generally favorable after complete surgical resection, with most patients remaining disease‑free PMC.
Histologically, MTSCC displays tightly packed, elongated tubules lined by cuboidal cells, interspersed with sheets of spindle‑shaped cells set in a pale mucinous background. Immunohistochemically, these tumors often express markers such as alpha‑methylacyl‑CoA racemase (AMACR) and cytokeratin 7, aiding differentiation from other RCC variants PMCBioMed Central.
Clinically, MTSCC tends to arise in adults with a wide age range (17–82 years) and shows a marked female predominance (female:male ≈4:1) WikipediaAtlas of Genetics in Oncology. Most tumors are discovered incidentally during imaging for unrelated reasons, but, when symptomatic, they mirror general RCC presentations.
Types
1. Classic MTSCC:
The classic variant features abundant extracellular mucin separating tightly packed tubular and spindle cell areas. Tubules are elongated with uniform cuboidal epithelial cells, while spindle cells are bland with minimal atypia. This variant generally follows an indolent course with low metastatic potential PMCAtlas of Genetics in Oncology.
2. Mucin‑Poor MTSCC:
In mucin‑poor variants, the mucinous matrix is scant or absent, and spindle cells predominate. These tumors may demonstrate higher cellularity and occasional mild nuclear atypia. Although many behave indolently, mucin‑poor cases have been linked to aggressive features and distant metastases in a minority of reports PMCSpandidos Publications.
3. Sarcomatoid Variant:
Rarely, MTSCC can undergo sarcomatoid transformation, characterized by marked spindle cell proliferation with pronounced atypia, mitotic figures, and necrosis. This high‑grade change correlates with rapid progression, metastasis, and poorer outcomes, necessitating close follow‑up BioMed Central.
Potential Causes and Risk Factors
End-Stage Renal Disease (ESRD):
Patients on long-term dialysis with acquired cystic kidney disease have up to a 50-fold increased risk of developing RCC subtypes, including rare forms like MTSCC. Chronic renal injury fosters epithelial proliferation and neoplastic transformation BioMed Central.Cigarette Smoking:
Smoking remains a leading modifiable risk factor for RCC. Carcinogens in tobacco can induce genetic mutations in renal epithelial cells, increasing the incidence of various RCC subtypes by up to 30–40% in smokers PubMedPMC.Obesity:
Excess body weight is associated with hormonal and inflammatory changes—such as elevated insulin and adipokines—that promote renal tumorigenesis. Paradoxically, obesity may also confer slightly better survival after diagnosis, known as the “obesity paradox” PubMedNew England Journal of Medicine.Hypertension:
High blood pressure damages renal microvasculature and fosters oxidative stress, significantly raising RCC risk independently of antihypertensive treatment. Hypertensive individuals have a higher likelihood of developing kidney tumors PubMedAmerican Heart Association Journals.Family History of Kidney Cancer:
A family history—especially in a first-degree relative—doubles the risk of RCC. Shared genetic susceptibilities or environmental exposures within families contribute to this increased risk American Cancer Society.Inherited Genetic Syndromes:
Hereditary conditions such as von Hippel–Lindau (VHL) disease, Birt‑Hogg‑Dubé syndrome, and tuberous sclerosis complex predispose to multicentric and bilateral renal tumors through germline mutations affecting tumor suppressor pathways Wikipedia.Chronic Kidney Disease (CKD):
Long-standing CKD, even without dialysis, increases RCC risk through persistent inflammation and renal parenchymal remodeling. Oxidative stress and reparative proliferation may lead to malignant transformation Verywell Health.Analgesic Abuse (NSAIDs):
Regular use of nonsteroidal anti‑inflammatory drugs, particularly at high doses, can cause interstitial nephritis and papillary necrosis, indirectly promoting carcinogenic processes in residual renal tissue Verywell Health.Occupational Chemical Exposures:
Workplace contact with trichloroethylene, asbestos, cadmium, and certain herbicides is implicated in RCC development. These agents can be nephrotoxic and mutagenic, elevating carcinoma risk The Times of IndiaTIME.Heavy Metal Exposure:
Environmental or occupational exposure to cadmium, chromium, or lead can damage renal epithelium and disrupt DNA repair mechanisms, heightening RCC susceptibility The Times of India.Dietary Factors:
Diets high in red and processed meats may increase RCC risk through inflammatory and oxidative pathways, whereas plant-based, anti-inflammatory diets appear protective Nature.Hepatitis C Virus (HCV) Infection:
Chronic HCV has been associated with extrahepatic malignancies, including RCC, possibly through systemic inflammatory and immune‑mediated mechanisms Wikipedia.Previous Cancer Treatments:
Prior exposure to therapeutic radiation or genotoxic chemotherapy for other malignancies can predispose to secondary RCC many years later through cumulative DNA damage Wikipedia.Age:
Incidence of RCC rises with age, peaking in the sixth and seventh decades of life. Cumulative genetic insults over time contribute to malignant transformation Wikipedia.Gender Predisposition:
Although classic RCC favors males, MTSCC shows a striking female predominance (≈80%), suggesting hormonal or genetic factors influence its development Atlas of Genetics in Oncology.
Common Symptoms
Asymptomatic/Incidental Findings:
Most MTSCC cases are discovered incidentally on imaging performed for unrelated reasons, reflecting the tumor’s often silent growth PMC.Hematuria (Blood in Urine):
Visible or microscopic hematuria occurs in a minority of patients, resulting from tumor invasion into renal collecting systems BioMed Central.Flank Pain:
Dull, persistent pain in the flank or back may indicate capsular stretching or local invasion by the tumor Wikipedia.Palpable Abdominal/Flank Mass:
A palpable lump may be felt on deep palpation in advanced or larger tumors, though this classic triad is rare (<1%) Uroweb.Unexplained Weight Loss:
Systemic catabolic effects of malignancy and inflammatory cytokines can lead to significant unintentional weight loss Wikipedia.Fever or Night Sweats:
Paraneoplastic cytokine release may cause low‑grade fevers or drenching night sweats in a subset of patients Wikipedia.Fatigue and Malaise:
Generalized weakness and a sense of discomfort often accompany systemic cancer effects Verywell Health.Anemia:
Chronic blood loss and tumor‑associated cytokines can suppress erythropoiesis, leading to anemia Wikipedia.Hypertension:
Tumor‑produced vasoactive substances and mass effect on renal vasculature can result in new or worsened high blood pressure Wikipedia.Paraneoplastic Syndromes:
MTSCC may, rarely, elicit paraneoplastic phenomena such as hypercalcemia, hepatic dysfunction, or neurologic syndromes, reflecting remote effects of tumor‑derived factors Verywell Health.
Diagnostic Tests
Physical Exam
Medical History and Physical Exam:
A thorough history assessing risk factors and a complete physical examination guide the diagnostic workup for suspected kidney tumors American Cancer Society.Inspection of Abdomen and Flanks:
Visual assessment may reveal asymmetry, distension, or superficial venous engorgement overlying a renal mass American Cancer Society.Palpation of Abdomen and Flanks:
Deep palpation can detect a flank or abdominal mass in larger tumors, though this finding is uncommon (<25%) TeachMeSurgery.
Manual Tests
Percussion for Costovertebral Angle (CVA) Tenderness:
Gentle percussion over the CVA elicits pain in some patients due to tumor‑induced inflammation or hemorrhage Medscape.Fine‑Needle Aspiration Cytology (FNAC):
Under imaging guidance, FNAC can collect cellular material for preliminary cytologic assessment, though it may be insufficient for subtype classification Wikipedia.Percutaneous Core Needle Biopsy (Renal Mass Biopsy):
Core needle biopsy under ultrasound or CT guidance provides tissue architecture for definitive histopathology, immunohistochemistry, and genetic studies Wikipedia.
Lab and Pathological Tests
Complete Blood Count (CBC):
Assesses for anemia, polycythemia, and thrombocytosis, which may reflect chronic bleeding or paraneoplastic effects Wikipedia.Comprehensive Metabolic Panel (CMP):
Measures renal and hepatic function, electrolytes, and calcium levels to evaluate organ involvement and paraneoplastic hypercalcemia Wikipedia.Urinalysis:
Detects microscopic or gross hematuria and casts, aiding early suspicion of renal pathology Wikipedia.Liver Function Tests (LFTs):
Evaluates liver involvement or paraneoplastic hepatic dysfunction Wikipedia.Histopathological Examination:
Microscopic evaluation of biopsy specimens confirms the characteristic tubular and spindle cell morphology Wikipedia.Immunohistochemistry Panel:
Markers such as AMACR, CK7, and EMA help differentiate MTSCC from papillary and other RCC variants BioMed Central.Cytogenetic Analysis:
Chromosomal studies reveal characteristic losses (e.g., chromosomes 1, 4, 6, 8, 9, 13, 14, 15, 18, 22) and absence of typical 3p deletions seen in clear cell RCC modernpathology.org.
Electrodiagnostic Tests
Electrocardiogram (ECG):
A 12‑lead ECG is routinely performed preoperatively to assess cardiac risk in patients undergoing nephrectomy AAFP.Electromyography (EMG):
EMG may be indicated when paraneoplastic neuropathy is suspected, evaluating nerve and muscle electrical activity PMC.Nerve Conduction Studies (NCS):
Used alongside EMG to quantify peripheral nerve involvement in paraneoplastic syndromes PMC.
Imaging Tests
Abdominal Ultrasonography:
First‑line imaging to detect solid renal masses, often revealing hypoechoic lesions and guiding further evaluation PMC.Contrast‑Enhanced Computed Tomography (CT):
Gold standard for characterizing renal masses’ size, enhancement patterns, and local extension; triple‑phase CT distinguishes solid tumors from cysts Renal and Urology News.Magnetic Resonance Imaging (MRI):
Useful in patients with contraindications to iodinated contrast; provides high‑resolution soft tissue contrast and staging information PMC.Positron Emission Tomography (PET) Scan:
Limited role in primary diagnosis but helpful in assessing metastatic disease when combined with CT (PET/CT) Frontiers.
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Last Updated: July 19, 2025.
