SoftTissue and Bone Sarcomas and Bone Metastases¶
Chapter 96 | Part 4: Oncology and Hematology · Part 4 – Oncology: Solid Tumors · Chapter 96
Key Clinical Points¶
- Li-Fraumeni syndrome (germline p53 mutation) predisposes to soft tissue sarcomas, osteosarcoma, brain tumors, and leukemia.
- Neurofibromatosis 1 (NF1) leads to malignant peripheral nerve sheath tumors (MPNST) arising from neurofibromas.
- Osteosarcoma: Predilection for metaphyses of long bones; characterized by 'sunburst' appearance and Codman's triangle.
- Ewing's Sarcoma: Occurs in diaphyseal long bones; 'onion peel' periosteal reaction; t(11;22) translocation creating EWS-FLI1 fusion gene.
- Gastrointestinal Stromal Tumors (GIST): Driven by activating c-kit or PDGFRA mutations; Imatinib is standard therapy.
- Soft Tissue Sarcoma Staging (AJCC 8th Ed): Based on Tumor size (T), Nodes (N), Metastasis (M), and Grade (G1-G4).
- Bone Metastases: Prostate, breast, and lung primaries account for 80% of cases; vertebrae are the most common site.
- Chondrosarcoma: Generally resistant to chemotherapy; surgical resection is mainstay; dedifferentiated variant responds to chemo.
- Advanced Soft Tissue Sarcoma: Doxorubicin and ifosfamide are mainstays; Pazopanib approved for advanced disease (excluding liposarcoma).
- Bone Metastasis Symptoms: Pain (gradual, worse at night), neurologic signs (cord compression), pathologic fracture, myelophthisis, and hypercalcemia.
1. DEFINITION & OVERVIEW¶
Sarcomas are rare mesenchymal neoplasms (<1% of all malignancies). They affect all age groups, with 15% in children and 40% in those over 55 years. Sarcomas are the fifth most common cause of cancer deaths in children.
Soft tissue sarcomas arise from muscles, tendons, fat, fibrous tissue, synovial tissue, vessels, and nerves. Approximately 60% occur in extremities (lower > upper), 30% in trunk (retroperitoneum 40%), and 10% in head/neck.
Bone sarcomas can also arise from soft tissues (e.g., extraskeletal osteosarcoma). The term 'malignant fibrous histiocytoma' has been replaced by undifferentiated pleomorphic sarcoma (UPS) and myxofibrosarcoma. Liposarcomas have variable behavior: well-differentiated variants lack metastatic potential, while dedifferentiated variants behave aggressively.
Rhabdomyosarcomas, Ewing's sarcoma, and small-cell sarcomas are more responsive to chemotherapy than other soft tissue sarcomas. GISTs (originating from interstitial cells of Cajal) are distinct from leiomyosaromas.
1.1 Classification of Soft Tissue Sarcomas¶
Soft tissue sarcomas are classified based on differentiation patterns:
• Rhabdomyosarcoma: Skeletal muscle fibers with cross-striations. • Leiomyosarcoma: Spindle cells resembling smooth muscle. • Liposarcoma: Adipocytes present. • Unclassified sarcomas: When differentiation cannot be determined.
GISTs are distinct from leiomyosarcomas. Most have c-kit mutations; 5–10% have PDGFRA mutations. Wild-type GISTs may involve SDH or IGF-I pathways.
2. EPIDEMIOLOGY¶
Approximately 13,400 new cases of soft tissue sarcomas occurred in the US in 2023 (incidence: 3/100,000). They constitute 0.7% of all cancers and 6.5% of childhood cancers.
Bone sarcomas are rarer (0.2% of malignancies), with 3970 new cases in the US in 2023. Osteosarcoma peaks in children/adolescents (2nd decade) and in older adults (secondary to radiation/Paget's disease). Ewing's sarcoma is common in adolescence, chondrosarcoma in middle-aged adults.
Males are affected 1.5–2× more often than females. Malignant transformation of benign tumors is rare except for MPNSTs in NF1 patients.
2.1 Incidence and Distribution¶
• Soft tissue sarcomas: 60% extremities (lower > upper), 30% trunk (retroperitoneum 40%), 10% head/neck. • Bone sarcomas: 0.2% of all malignancies. • Osteosarcoma: 60% children/adolescents, 10% 3rd decade, 5th/6th decade secondary to radiation/Paget's. • Ewing's Sarcoma: Peak in 2nd decade. • Chondrosarcoma: Peak in 4th–6th decades.
3. ETIOLOGY & PATHOPHYSIOLOGY¶
Etiologic factors include trauma, chemical carcinogens (asbestos, dioxin), immunosuppression, and genetic syndromes:
• Li-Fraumeni syndrome: Germline p53 mutation; predisposes to sarcomas, breast cancer, osteosarcoma, brain tumors. • Neurofibromatosis 1 (NF1): Gene on chromosome 17; malignant transformation of neurofibromas to MPNSTs. • Retinoblastoma: RB1 mutations linked to osteosarcoma in survivors.
Molecular mechanisms include: • Synovial sarcomas: t(X;18) translocation involving SYT and SSX genes. • GISTs: c-kit or PDGFRA mutations. • Ewing's sarcoma: t(11;22) creating EWS-FLI1 fusion gene.
3.1 Molecular Mechanisms¶
• Synovial sarcomas: 90% have t(X;18)(p11;q11), with SSX2 translocations associated with better survival. • GISTs: c-kit mutations (90%), PDGFRA (5–10%), or SDH/IGF-I pathway in wild-type cases. • Ewing's sarcoma: t(11;22) creates EWS-FLI1 fusion gene. p30/32 is a cell-surface marker.
4. CLINICAL FEATURES¶
Common presentations include asymptomatic masses, pain/swelling, or mechanical symptoms from nerve/muscle compression.
Bone metastases present with gradual-onset pain (worse at night), neurologic signs (spinal cord compression), pathologic fractures, myelophthisis, or hypercalcemia. Radiographic features vary by tumor type:
• Osteosarcoma: Sunburst appearance, Codman's triangle. • Ewing's sarcoma: 'Onion peel' periosteal reaction. • Chondrosarcoma: Lobular appearance with calcification.
4.1 Bone Metastasis Symptoms¶
• Pain: Gradual onset, localized, worse at night. • Neurologic signs: Spinal cord compression. • Fracture: Pathologic fracture. • Myelophthisis: Marrow replacement. • Hypercalcemia: Seen in bony destruction.
5. DIFFERENTIAL DIAGNOSIS¶
Benign vs malignant bone tumors:
• Benign: Enchondroma, osteochondroma, chondroblastoma, chondromyxoid fibroma, osteoid osteoma, osteoblastoma, fibroma, desmoplastic fibroma, hemangioma, giant cell tumor. • Malignant: Osteosarcoma, chondrosarcoma, Ewing's sarcoma, UPS. • Rare malignant: Chordoma, malignant giant cell tumor, adamantinoma, hemangioendothelioma.
Ewing's sarcoma may mimic lymphoma or rhabdomyosarcoma. p30/32 is a specific marker.
5.1 Benign vs Malignant Bone Tumors¶
• Benign: Enchondroma, osteochondroma, chondroblastoma, chondromyxoid fibroma, osteoid osteoma, osteoblastoma, fibroma, desmoplastic fibroma, hemangioma, giant cell tumor. • Malignant: Osteosarcoma, chondrosarcoma, Ewing's sarcoma, UPS. • Rare Malignant: Chordoma, malignant giant cell tumor, adamantinoma, hemangioendothelioma.
6. INVESTIGATIONS & DIAGNOSIS¶
Imaging modalities:
• Plain radiographs: Initial screening for destructive lesions, moth-eaten appearance, sunburst appearance, Codman's triangle. • MRI: Best for extremity/head/neck tumors; defines intramedullary and soft tissue extension. • CT: For chest/abdomen/retroperitoneal tumors; assesses bone destruction/calcification. • Chest CT: Detects lung metastases. • Bone scan/FDG-PET: For bone metastases (osteosarcomas are PET-avid).
Biopsy is critical: core-needle or open biopsy to avoid compromising future resection.
6.1 Imaging Modalities¶
• Plain radiographs: Destructive lesion, moth-eaten appearance, sunburst appearance, Codman's triangle. • MRI: Extremity/head/neck tumors; intramedullary and soft tissue extension. • CT: Chest/abdomen/retroperitoneal tumors; bone destruction/calcification. • Chest CT: Lung metastases detection. • Bone scan/FDG-PET: Bone metastases (osteosarcomas are PET-avid).
7. MANAGEMENT & TREATMENT¶
Treatment depends on AJCC stage:
• Stage I: Surgery alone. • Stage II: Adjuvant radiation. • Stage III: Neoadjuvant/adjuvant chemotherapy. • Stage IV: Systemic therapy (doxorubicin, ifosfamide, Pazopanib for advanced disease).
Surgical principles: • Wide excision with negative margins. • Limb-sparing surgery is preferred if feasible. • Radiation improves local control rates.
Chemotherapy regimens: • Ewing's sarcoma: Doxorubicin, cyclophosphamide/ifosfamide, etoposide, vincristine. • Soft tissue sarcomas: Anthracycline + ifosfamide with growth factor support (improves 19% survival in high-risk cases). • Chondrosarcoma: Surgery for most; dedifferentiated variant responds to chemo.
7.1 Drug Therapy for Soft Tissue Sarcomas¶
• Doxorubicin: Non-small-cell sarcomas (anthracycline); improves local control and disease-free survival. • Ifosfamide: High-risk soft tissue sarcomas; combined with doxorubicin; 6% survival advantage in meta-analysis. • Pazopanib: Advanced soft tissue sarcomas (excluding liposarcoma). • Regorafenib: Progressive metastatic sarcomas; improved progression-free survival vs placebo.
7.2 Drug Therapy for Bone Sarcomas¶
• Ewing's sarcoma: Doxorubicin, ifosfamide, etoposide, vincristine. • Osteosarcoma: Radioresistant; surgery + chemotherapy (doxorubicin/ifosfamide). 60–80% survival in extremity cases. • Chondrosarcoma: Surgery for most; dedifferentiated variant responds to chemo. • UPS: Managed similarly to osteosarcoma.
8. PROGNOSIS & COMPLICATIONS¶
Prognosis varies by tumor type and stage:
• Soft tissue sarcomas: 5-year survival ~60–70% for localized disease; metastatic cases largely incurable (20% achieve long-term remission with complete response). • Osteosarcoma: 60–80% survival in extremity cases. • Ewing's sarcoma: 60–70% cure rate for localized tumors. • Chondrosarcoma: Indolent; surgery is mainstay. Dedifferentiated variant responds to chemo.
9. SPECIAL CONSIDERATIONS¶
Genetic syndromes:
• Li-Fraumeni syndrome: Germline p53 mutation; increased risk of sarcomas, breast cancer, brain tumors. • Neurofibromatosis 1 (NF1): Malignant transformation of neurofibromas to MPNSTs. • Retinoblastoma: RB1 mutations linked to osteosarcoma in survivors.
9.1 Genetic Syndromes¶
• Li-Fraumeni syndrome: Germline p53 mutation; predisposes to sarcomas, breast cancer, brain tumors. • Neurofibromatosis 1 (NF1): Gene on chromosome 17; malignant transformation of neurofibromas to MPNSTs. • Retinoblastoma: RB1 mutations linked to osteosarcoma in survivors.
10. KEY PEARLS & CLINICAL TRAPS¶
Diagnostic clues:
• Osteosarcoma: Sunburst appearance, Codman's triangle on radiographs. • Ewing's sarcoma: 'Onion peel' periosteal reaction; t(11;22) translocation. • GISTs: c-kit or PDGFRA mutations; liver metastases common. • Chondrosarcoma: Lobular calcification on radiographs; resistant to chemo. • Soft tissue sarcomas: Wide excision with negative margins is critical for local control.
Reference Tables¶
TABLE 96-1 American Joint Commission on Cancer Staging System for Sarcomas, Eighth Edition T1 T2 T3 T4 N0 N1 M0 M1…¶
Harrison's 22e, p.728
| T1 | Tumor ≤5 cm in greatest dimension |
|---|---|
| T3 | Tumor >10 cm and ≤15 cm in greatest dimension |
| N0 | No regional lymph node metastasis or unknown lymph node status |
| M0 | No distant metastasis |
| Stage Groups | |
| Stage IA | T1; N0; M0; G1 |
| Stage II | T1; N0; M0; G2/3 |
| Stage IIIB | T3, T4; N0; M0; G2/3 |
TABLE 96-2 Staging System for Bone Sarcomas Primary tumor (T)¶
Harrison's 22e, p.729
| Primary tumor (T) | TX | Primary tumor cannot be assessed | ||
|---|---|---|---|---|
| T0 | No evidence of primary tumor | |||
| T1 | Tumor ≤8 cm in greatest dimension | |||
| T2 | Tumor >8 cm in greatest dimension | |||
| T3 | Discontinuous tumors in the primary bone site |
|||
| NX | ||||
| N0 | ||||
| N1 | ||||
| Distant metastasis (M) | MX | Distant metastasis cannot be assessed | ||
| M0 | No distant metastasis | |||
| M1 | Distant metastasis | |||
| M1a | Lung | |||
| M1b | Other distant sites | |||
| GX | ||||
| G1 | ||||
| G2 | ||||
| G3 | ||||
| G4 | ||||
| Stage Grouping | ||||
| Stage IA | T1 | N0 | M0 | G1,2 low grade |
| T2 | N0 | M0 | ||
| Stage IIA | T1 | N0 | M0 | G3,4 high grade |
| T2 | N0 | M0 | ||
| Stage III | T3 | N0 | M0 | Any G |
| Any T | N0 | M1a | ||
| Stage IVB | Any T | N1 | Any M | Any G |
| Any T | Any N | M1b | Any G |