PA32.2-3 | Bone & Soft Tissue Tumors — Summary & Reflection

REFLECT

You have covered the two major competencies for bone and soft tissue tumors. Before moving to the micro-quiz and summary, take 5 minutes to work through these questions in your own words — close the notes and answer from memory.

1. A 16-year-old presents with knee pain; X-ray shows a metaphyseal lesion with a sunburst pattern and Codman triangle. Walk through the pathogenesis, histologic criterion, and most likely first site of metastasis.
2. An elderly man (65 years) has back pain. X-ray shows multiple dense, sclerotic vertebral bodies. What primary tumor is most likely, and are these osteolytic or osteoblastic metastases — why?
3. Draw from memory the contrast table: Osteosarcoma vs GCT vs Ewing sarcoma — age, site (epiphysis/metaphysis/diaphysis), key radiologic sign, key histologic sign.
4. Which soft tissue sarcoma is diagnosed in the youngest patients, what is its histologic hallmark, and why does it spread to lymph nodes?
5. You are in OPD. A 45-year-old woman has a painless, soft, mobile subcutaneous mass in her upper arm for 3 years. What is the most likely diagnosis, and what single histologic finding would make you revise this to malignant?

KEY TAKEAWAYS

Bone Tumors — The Essential Map

• Osteoid osteoma: <2 cm, nocturnal pain relieved by aspirin, lucent nidus with sclerotic halo; benign.
• Osteosarcoma: most common primary bone malignancy; teen, metaphysis around knee; Codman triangle + sunburst; lace-like malignant osteoid; RB1/TP53 loss; hematogenous lung mets; chemo-responsive.
• Osteochondroma: most common benign bone tumor; bony excrescence with cartilage cap from metaphysis; cortex + medullary canal continuous with host bone.
• Enchondroma: intramedullary; short tubular bones; rings-and-arcs calcification; Ollier/Maffucci syndromes increase malignant risk.
• Chondrosarcoma: second most common primary malignant bone tumor; adults 40–70 yrs; pelvis/proximal femur; rings-and-arcs + endosteal scalloping; resistant to chemo/radiation — surgery only; IDH1/2 mutations.
• Giant cell tumor: skeletally mature adults 20–40 yrs; epiphysis; soap-bubble lytic; osteoclast-like giant cells + mononuclear stromal cells; H3F3A mutation; treated with denosumab.
• Ewing sarcoma: children 5–20 yrs; diaphysis; onion-skin periosteal reaction; small round blue cells; t(11;22) EWSR1-FLI1; CD99+; mimics osteomyelitis (fever).
• Metastatic bone disease: most common overall malignancy in bone; BBC KT (Breast, Bronchus, Colon, Kidney, Thyroid) = lytic; Prostate = blastic; axial skeleton + proximal femur; complications: pathological fracture, hypercalcemia, cord compression.

Soft Tissue Tumors — The Essential Map

• Lipoma/Liposarcoma: lipoma = most common benign soft tissue tumor; liposarcoma = most common adult soft tissue sarcoma; lipoblast = hallmark of malignancy; retroperitoneum is the danger site.
• Rhabdomyosarcoma: most common soft tissue sarcoma in children; embryonal (botryoid) vs alveolar (PAX3-FOXO1); desmin/myogenin+; spreads to lymph nodes AND lung.
• Leiomyosarcoma: adults; retroperitoneum/uterus; cigar-shaped nuclei; SMA+.
• Fibrosarcoma: herringbone/chevron pattern; spindle cells; rare in pure form today.
• Synovial sarcoma: young adults 15–35 yrs; periarticular; t(X;18) SYT-SSX; biphasic (glands + spindle cells); TLE1+; calcification; spreads to lymph nodes.

Universal sarcoma rule: hematogenous spread to lungs (exceptions: RMS + synovial sarcoma also spread lymphatically).