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a rare malignant tumor of synovial origin, most commonly involving the knee joint and composed of spindle cells usually enclosing slits or pseudoglandular spaces that may be lined by radially disposed epitheliallike cells.
synovial sarcomaA mesenchymal spindle cell tumour which comprises ±10% of all soft-tissue sarcomas. It is most common in young (age 20 to 40) males, and occurs most commonly around the large joints—knee, ankle, foot, 60% in the legs, 23% in upper extremity. However, it can go any place, as cases have been reported in the penis, lung, vulva, abdominal wall, etc.
50% 5-year survival; extensively calcified synovial sarcomas have a higher (84%) 5-year survival; 40% metastasise to lungs, bone-regional nodes.
Good prognostic factors
Children; < 5cm; <10 mitoses/10hpf; no necrosis; complete excision in first attempt.
Older age, larger size (especially, > 35 cm), necrosis, vascular invasion, high Ki-67 index, high-grade nuclei, poorly differentiated areas, known recurrence.
Synovial sarcoma, histologic types
• Distinct epithelial and spindle cell components.
DiffDx, Spindle cell type
Malignant peripheral-nerve sheath tumour, schwanoma, solitary fibrous tumour, fasciitis.
DiffDx, Glandular cell type
Ewing sarcoma and other small round cell tumours.