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Pathology - Malignant Bone Tumors
I. Metastatic Bone Tumors
A. Osteosarcoma
I. Metastatic Bone Tumors
- Prevalence: The vast majority of malignant bone tumors are metastatic (secondary), meaning they spread from another primary cancer site.
- Primary Sources: Common primary sites include lung, breast, kidney, thyroid, and prostate carcinomas.
- Bone Destruction: Most metastatic bone tumors are osteolytic, meaning they break down bone tissue. An exception is prostate cancer metastases, which are typically osteosclerotic (stimulate new bone formation).
- Hypercalcemia: Bone metastases are a frequent cause of hypercalcemia (high blood calcium levels).
A. Osteosarcoma
- Definition: A malignant bone-forming tumor; the most common primary malignant bone tumor.
- Demographics: Most commonly affects individuals aged 5-25, presenting with persistent deep pain in a long bone, often accompanied by a palpable mass. Elderly cases are often secondary to Paget's disease.
- Histology: Composed of atypical cells that produce osteoid (unmineralized bone matrix).
- Spread: Highly malignant with early and rapid hematogenous (bloodstream) spread, primarily to the lungs.
- Prognosis: Strongly dependent on response to preoperative therapy. Responders have excellent survival (80-90%), while non-responders have poor survival (<15%).< />pan>
- Definition: A malignant cartilage-forming tumor; the second most common primary malignant bone tumor.
- Demographics: Primarily affects adults over 50 years old.
- Location: Most common in pelvic bones.
- Histology: Composed of variably atypical cells producing a cartilaginous matrix. Graded 1-3, with most being grades 1 or 2.
- Prognosis: Histological grade is the key prognostic factor. Grade 1 tumors have a 90% 5-year survival rate, while grades 2 and 3 have closer to 50%.
- Definition: A malignant round cell tumor of bone.
- Demographics: Most common in children and adolescents under 20 years old.
- Presentation: Presents with pain and a mass in long bones, pelvis, or ribs.
- Histology: Small round tumor cells with scant cytoplasm; may form rosette-like structures; necrosis is common.
- Genetics: Often shows a characteristic t(11;22) chromosomal translocation fusing the EWS and FLI1 genes.
- Prognosis: Survival rates are less than 50%, depending on stage, location, and tumor size.
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