Pathology: synovial sarcoma
Synovial sarcoma
Cellular; sheets and nests of polygonal cells and fascicles of spindle cells
Scant amphophilic cytoplasm
Round-ovoid nuclei with crowding, mild pleomorphism; mitotic activity
Wiry collagen interspersed between the cells; thin-walled, branching vessels; necrosis
RNA-seq: SS18::SSX2 gene fusion
Synovial sarcoma
Cellular; spindle cell fascicles
Eosinophilic cytoplasm with indistinct cell borders
Ovoid nuclei with striking palisading, mild pleomorphism; mitotic activity
Abundant necrosis
RNA-seq: SS18::SSX1 gene fusion
Synovial sarcoma
Cellular; spindle cell fascicles
Pale eosinophilic cytoplasm with indistinct cell borders
Ovoid nuclei with striking palisading, mild pleomorphism; mitotic activity
RNA-seq: SS18::SSX2 gene fusion
Synovial sarcoma
Cellular; biphasic; spindle-epithelioid cells in nests and fascicles with areas of gland formation
Abundant pale amphophilic cytoplasm
Plump ovoid nuclei with crowding, prominent nucleoli and mild pleomorphism; mitotic activity
Wiry collagen interspersed between the cells; thin-walled, branching vessels; necrosis
IHC: keratin (AE1/AE3)
RNA-seq: SS18::SSX2 gene fusion
Synovial sarcoma
Cellular; sheets-nests of polygonal cells
Scant pale amphophilic cytoplasm
Round-ovoid nuclei with mild pleomorphism; mitotic activity
Wiry collagen interspersed between the cells; prominent branching thin-walled vasculature
IHC: epithelial membrane antigen
RNA-seq: SS18::SSX2 gene fusion
Synovial sarcoma, biphasic
Cellular; biphasic; spindle cell fascicles with epithelioid gland formation
Abundant pale amphophilic cytoplasm
Plump ovoid nuclei with crowding, prominent nucleoli and mild pleomorphism; inconspicuous mitotic activity
Dystrophic calcification
RNA-seq: SS18::SSX1 gene fusion
Synovial sarcoma, biphasic
Cellular; biphasic; spindle cell fascicles with epithelioid gland formation
Abundant pale amphophilic cytoplasm
Ovoid-round nuclei with minimal pleomorphism; inconspicuous mitotic activity
RNA-seq: SS18::SSX1 gene fusion
Synovial sarcoma
Spindle cells with herringbone pattern
Amphophilic cytoplasm
Plump ovoid nuclei with crowding, mild pleomorphism; mitotic activity
Wiry collagen interspersed between the cells; occasional broad bands of collagen; focal myxoid stroma; prominent dystrophic calcification
RNA-seq: SS18:SSX1 gene fusion
Synovial sarcoma
Cellular; spindle cells with herringbone-storiform pattern
Scant amphophilic cytoplasm
Plump ovoid nuclei, minimal pleomorphism; mitotic activity
Focal myxoid stroma
RT-PCR: SS18::SSX gene fusion
Synovial sarcoma
Spindle-stellate cells with herringbone-fascicular pattern
Scant amphophilic cytoplasm
Hyperchromatic ovoid nuclei, minimal pleomorphism; inconspicuous mitotic activity
Myxoid stroma
RNA-seq: SS18:SSX2 gene fusion
Synovial sarcoma
Cellular; spindle cells with herringbone pattern
Minimal eosinophilic cytoplasm with long tapering processes
Elongated fusiform nuclei with mild pleomorphism; inconspicuous mitotic activity
Prominent wiry collagen interspersed between the cells
RT-PCR: SS18::SSX gene fusion
Synovial sarcoma
Spindle-ovoid cells with vague fascicular pattern
Pale eosinophilic cytoplasm with indistinct cell borders
Monomorphic ovoid nuclei; rare mitotic activity
Nodules of hyaline stroma (reminiscent of cartilage / osteoid)
RNA-seq: SS18:SSX2 gene fusion
Synovial sarcoma
Cellular; sheets-nests of round cells
Scant amphophilic cytoplasm
Round-ovoid nuclei with mild pleomorphism; mitotic activity
Prominent branching thin-walled vasculature
IHC: keratin (AE1/AE3)
RT-PCR: SS18::SSX gene fusion