Osteosarcoma is a cancer that starts in the bone-making cells. These cells normally build the hard mineral part of bone. In osteosarcoma they grow out of control and make abnormal bone tissue. It most often affects the long bones near the knee or shoulder in teenagers and young adults, but it can occur at any age. Cure usually needs two things: strong chemotherapy and complete surgery to remove all tumor that can be safely taken out. Without chemo, the cancer almost always spreads, often to the lungs. With modern care, survival has improved, but progress has been slow since the 1980s. Cancer.gov
Osteosarcoma is a fast-growing bone cancer that usually starts in the long bones (like the femur near the knee). Treatment most often combines chemotherapy before surgery (to shrink and control the tumor), limb-saving surgery when possible, and more chemotherapy after surgery. The standard baseline drug combination in many countries is called “MAP” (high-dose methotrexate, doxorubicin, and cisplatin). Radiation is used only in selected situations, because most osteosarcomas are not very sensitive to radiation. Care is delivered by a sarcoma team that includes medical oncologists, orthopedic oncologic surgeons, pathologists, radiologists, rehabilitation specialists, and supportive-care experts. Cancer.gov+1
Osteosarcoma is a cancer that starts in bone-forming cells. These cells are called osteoblasts. In osteosarcoma, the cells grow in a fast and disorganized way. They make abnormal bone (called osteoid) inside the tumor. This is the key feature doctors see under the microscope. Osteosarcoma is most common in teenagers and young adults. It often starts near the knee (the lower end of the femur or the upper end of the tibia) or near the shoulder (the upper humerus). It can happen in any bone, and in rare cases in soft tissue outside a bone (extraskeletal osteosarcoma). It tends to grow quickly. If not treated early, it can spread to the lungs or other bones. Today, with proper care, many people can be cured. Care usually involves chemotherapy plus limb-sparing surgery. But this article focuses on names, types, causes (risk factors), symptoms, and diagnostic tests.
Other names
Other names for osteosarcoma include: osteogenic sarcoma, primary malignant bone tumor producing osteoid, and when it arises in soft tissue, extraskeletal osteosarcoma. Older medical papers may say conventional osteosarcoma for the common type, and use terms like parosteal or periosteal osteosarcoma for special surface types. When the tumor develops in a bone already changed by another disease (for example, Paget disease of bone) or after radiation, it may be called secondary osteosarcoma.
Types
Conventional (high-grade) intramedullary osteosarcoma.
This is the most common type. “Intramedullary” means it starts in the central part of the bone. It is a high-grade cancer, which means the cells look very abnormal and grow fast. Doctors often sub-classify it by what the cells make most: osteoblastic (more bone-like matrix), chondroblastic (more cartilage-like areas), or fibroblastic (more fibrous tissue). All three behave as high-grade tumors.
Telangiectatic osteosarcoma.
This type has many blood-filled spaces inside the tumor, like a sponge. On imaging it can look like a cyst. Under the microscope it is still a high-grade osteosarcoma. It needs the same strong treatment as other high-grade types.
Small-cell osteosarcoma.
This rare type has small, round cancer cells. It can look like Ewing sarcoma on first glance, but it still makes osteoid (abnormal bone), so it is an osteosarcoma. It is aggressive and needs the standard chemotherapy plus surgery.
Low-grade central osteosarcoma.
This is rare and grows more slowly. It still needs surgery, but chemotherapy may not be needed if it is truly low grade and completely removed. Correct diagnosis is important, because treatment is different from high-grade tumors.
Parosteal osteosarcoma.
This tumor grows on the outer surface of the bone under the periosteum (the bone covering). It is usually low grade and slow growing. It most often affects the back of the lower thigh bone (posterior distal femur). Surgery with wide removal is the main treatment.
Periosteal osteosarcoma.
This surface tumor is usually intermediate grade and shows more cartilage components. It arises from the bone surface and often causes a sunburst-like reaction on X-ray. Treatment is surgery; some cases also receive chemotherapy.
High-grade surface osteosarcoma.
This rare surface tumor is high grade. It needs aggressive treatment like conventional osteosarcoma: chemotherapy plus wide surgery.
Secondary osteosarcoma (after bone disease or radiation).
Sometimes osteosarcoma starts in a bone already changed by Paget disease or after radiation therapy for another condition. These tumors are often high grade and need full treatment.
Extraskeletal osteosarcoma.
This very rare type starts in soft tissues instead of bone, but the tumor cells still make osteoid. It is treated as a soft tissue sarcoma with surgery and often chemotherapy.
Doctors classify osteosarcoma by its location in the bone, how it looks under the microscope, and its grade.
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Conventional (intramedullary) osteosarcoma – the common type that starts in the middle of the bone and is high grade. It often shows one dominant pattern (see 2–4). PubMed
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Osteoblastic subtype – the tumor makes lots of bony matrix (osteoid). Bones may look very dense on x-ray. mss-ijmsr.com
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Chondroblastic subtype – the tumor also makes cartilage-like tissue.
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Fibroblastic subtype – the tumor has spindle cells and less bony matrix.
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Telangiectatic osteosarcoma – pockets of blood inside the tumor; can look like a benign cyst but is aggressive. mss-ijmsr.com
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Small-cell osteosarcoma – rare; the cancer cells are small and can look like Ewing sarcoma, but they make osteoid. mss-ijmsr.com
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High-grade surface osteosarcoma – high-grade tumor that grows on the outer surface of bone.
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Periosteal osteosarcoma – intermediate-grade tumor on the surface, often with cartilage features.
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Parosteal osteosarcoma – low-grade surface tumor; tends to grow slowly and may be cured with wide surgery if found early.
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Secondary osteosarcoma – arises in bone after radiation therapy, in Paget disease, or in areas of old bone injury or disease. PubMed
Causes and risk factors
We use “cause” in everyday speech, but for most people, these are risk factors. Having a risk factor does not mean you will get osteosarcoma. Many patients have none of these.
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Teenage growth spurt – fast bone growth may raise risk; tumors often start near growth plates. Cancer.gov
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Male sex – males are affected slightly more often. Cancer.org
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Tall height in adolescence – linked in some studies to higher risk, likely related to growth velocity. Cancer.org
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Inherited RB1 mutation (hereditary retinoblastoma) – very strong risk for bone sarcomas. PubMed
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TP53 mutation (Li-Fraumeni syndrome) – greatly increases risk of many cancers, including osteosarcoma. PubMed
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RECQL4 mutations (Rothmund-Thomson syndrome) – raised osteosarcoma risk. PubMed
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Bloom syndrome (BLM mutations) – genomic instability; higher sarcoma risk. PubMed
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Werner syndrome – premature aging disorder; sarcoma risk increased. PubMed
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Diamond–Blackfan anemia – congenital anemia with cancer risk; osteosarcoma reported. PubMed
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Paget disease of bone – abnormal bone turnover in older adults can transform into osteosarcoma. Cancer.org
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Previous high-dose radiation to bone – classic cause years after treatment. Cancer.gov
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Prior chemotherapy with alkylators – small increased risk when combined with radiation. Cancer.gov
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Bone infarcts (dead bone areas) – rare setting for secondary osteosarcoma. PubMed
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Chronic bone disease (e.g., fibrous dysplasia) – rare malignant change reported. PubMed
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Implants or foreign bodies – very rare case reports after long latency. PubMed
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Long-standing bone injury with abnormal healing – not a proven cause but sometimes noted in histories. Cancer.org
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Family history of sarcoma – can signal a hereditary syndrome (see items 4–8). PubMed
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Older age with Paget disease – a second peak of cases occurs later in life due to this condition. Cancer.org
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Certain environmental exposures – weak evidence overall; no clear everyday exposure is confirmed as a major cause. Cancer.org
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Previous benign bone tumor in the same area – very rare transformation; pathology must prove new osteoid-forming malignancy. PubMed
Symptoms and signs
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Bone or joint pain – the most common symptom; often worse at night or with activity. It can be mistaken for “growing pains.” Mayo Clinic+1
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Swelling or a lump over the bone – may appear weeks after the pain starts. Cancer.org
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Warmth and tenderness over the area – due to tumor growth and inflammation. Cancer.org
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Stiff joint or reduced movement – if the tumor is near a joint. Cancer.org
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Limp or change in gait – when a leg bone is involved. Cancer.org
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Sudden bone break (pathologic fracture) – the bone can break with minor injury because the tumor weakens it. Mayo Clinic
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Deep ache at rest – pain can continue even when you are not moving. Cancer.org
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Pain that wakes you from sleep – common red flag in teenagers with knee pain. Cancer.org
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Numbness or tingling – if the tumor presses on nearby nerves.
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Skin stretching with shiny surface – when the mass grows near the skin.
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Visible veins over the lump – from increased blood flow.
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Muscle wasting – less use of the limb over time.
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Fatigue – from pain, poor sleep, or anemia.
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Fever or weight loss (uncommon) – can occur but are not specific.
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Breathlessness or cough – if cancer has spread to the lungs (advanced). Cancer.org
Diagnostic tests
Diagnosis is best handled at a sarcoma center. A biopsy should be planned by the surgeon who will do the definitive surgery to avoid problems later. Cancer.gov
A) Physical examination
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Inspection of the limb – the doctor looks for swelling, a lump, skin changes, and limb alignment. This helps decide which imaging to do first and whether the tumor is near a joint. NCCN
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Palpation (feeling the area) – checks for warmth, tenderness, firmness, and whether the mass is fixed to the bone. Pain on pressing the bone is common. NCCN
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Range-of-motion and function tests – the doctor gently moves the nearby joint to see limits, pain, or catching. This guides therapy planning and physical therapy needs. NCCN
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Neurovascular exam – checks pulses, capillary refill, and nerve function in the limb because large tumors can press on vessels and nerves. Findings affect surgery planning. NCCN
B) Manual/bedside assessments
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Gait assessment and limp check – watching how you walk shows pain level and bone strength risk.
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Point-tenderness and percussion pain – careful tapping over the bone can localize the lesion.
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Strength testing – mild weakness may be due to pain; severe weakness suggests nerve involvement and needs urgent imaging.
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Measurement of limb size and length – compares swelling, muscle loss, or bone length differences in growing teens.
(These bedside checks do not diagnose cancer by themselves; they direct imaging and urgent care when needed, as reflected in patient pathways.) NCCN
C) Laboratory and pathologic tests
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Complete blood count (CBC) – looks for anemia or infection; baseline before chemotherapy.
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Serum alkaline phosphatase (ALP) – often higher in active bone disease and can be elevated in osteosarcoma; high levels can relate to prognosis. JNCCN
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Lactate dehydrogenase (LDH) – may be elevated and has prognostic value in some studies. JNCCN
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Basic metabolic panel and liver tests – needed to plan safe chemotherapy. JNCCN
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Pregnancy test (when applicable) – required before some imaging and chemotherapy. NCCN
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Biopsy (core needle or open surgical) – the key test. A pathologist confirms osteosarcoma by finding malignant cells that make osteoid. Biopsy should be done by or in coordination with the sarcoma surgeon to avoid contaminating tissues that need to be saved. Cancer.gov
D) Electrodiagnostic and related assessments
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Electromyography/nerve conduction studies (EMG/NCS) – rarely used; can document nerve compression from a large tumor when symptoms suggest nerve injury and help with rehab planning.
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Electrocardiogram (ECG) – not for diagnosis of the tumor itself, but often done before anthracycline chemotherapy to check heart rhythm and baseline status per guideline-based workup. JNCCN
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Echocardiography (heart ultrasound) – again not diagnostic of the tumor, but used before and during treatment to monitor heart function with doxorubicin-based regimens. This is standard supportive testing in bone cancer care pathways. JNCCN
E) Imaging tests
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Plain x-ray of the bone – the first and very important test. It can show a destructive lesion, new bone formation, a “sunburst” pattern, or a lifted periosteum (Codman triangle). These patterns suggest an aggressive bone tumor. Cancer.org
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MRI of the entire bone and nearby joint – best test to define the true size, the marrow and soft-tissue spread, skip lesions in the same bone, and the relation to nerves and vessels. Guides surgery. NCCN
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CT scan of the chest – essential for staging because the lungs are the most common site of spread. NCCN
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Bone scan (nuclear medicine) – looks for active bone changes in the rest of the skeleton; may be skipped if a PET-CT is planned. Cancer.org
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FDG-PET/CT – helps assess the whole body for spread and treatment response in some centers; it can reduce the need for a bone scan. Cancer.org
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CT of the primary bone – sometimes used to see mineralization details and to plan surgery, especially when MRI is limited. NCCN
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Targeted imaging for special sites – for example, panoramic dental x-ray or maxillofacial CT for jaw tumors, or whole-spine MRI if symptoms suggest other bone involvement. Care teams choose these based on location and symptoms. NCCN
