Synovial Sarcoma

t(X;18;p11;q11) is required for the identification of such tumors as synovial sarcoma
2 of following in at least 2 low power fields proposed for designation by de Silva
- Cellular areas with nuclear crowding
- Nuclear irregularity
- Prominent nucleoli
- Irregular, clumped chromatin
Other frequently associated features
- Increased mitotic figures (>10/10hpf)
- Necrosis
- Presence of hemangiopericytoma like vessels
Cell types may be epithelioid, spindled, small round
Occasional patterns
- Herringbone
- Desmoplastic stroma surrounding nodules of cells
- Cord or strands of cells
- Pseudorosettes
- Rhabdoid cells
- Clear cells
Uniform, small round to spindle cells
- Solid, closely packed cells
- Resembles small round blue cell tumors of childhood
May be focal or pure
- May be seen focally in up to 46% of cases
- Pure pattern requires cytogenetic confirmation for diagnosis
Keratin and EMA reported 33-100% positive, frequently focal
Presence of at least 2 low power fields or 20% by area indicates worse prognosis
- Increased recurrence, metastasis, death
- Increased percentage associated with increasingly worse behavior