Cellular; spindle-epithelioid cells in nests and fascicles with areas of gland-like formation
Abundant pale amphophilic cytoplasm
Plump ovoid nuclei with crowding, prominent nucleoli and mild pleomorphism; mitotic activity
IHC: keratin (AE1/AE3)
RNA-seq: SS18::SSX1 gene fusion
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
IHC: keratin (AE1/AE3)
RNA-seq: SS18::SSX2 gene fusion
Cellular; biphasic; spindle-epithelioid cells in nests and fascicles
Abundant pale eosinophilic cytoplasm
Plump ovoid nuclei with small nucleoli and mild pleomorphism; conspicuous mitotic activity
Scant collagenous stroma
RNA-seq: SS18::SSX1 gene fusion
Cellular; biphasic; spindle-epithelioid cells in nests and fascicles
Abundant pale eosinophilic cytoplasm
Plump ovoid nuclei with small nucleoli and mild pleomorphism
Scant collagenous stroma
RNA-seq: SS18::SSX1 gene fusion
Cellular; spindle cells with a herringbone pattern
Scant amphophilic cytoplasm
Plump ovoid nuclei with crowding, mild pleomorphism; mitotic activity
Wiry collagen interspersed between the cells; focal myxoid stroma
IHC: H3K27me3
RNA-seq: SS18::SSX2 gene fusion
Lobulated; loose fascicles of spindle-stellate cells
Scant pale eosinophilic cytoplasm
Ovoid nuclei with mild pleomorphism; mitotic activity
Myxoid-collagenous stroma with wiry collagen between the cells; metaplastic bone and cartilage; dystrophic calcification
IHC: S100, keratin (AE1/AE3), epithelial membrane antigen
RNA-seq: SS18::SSX1 gene fusion
Variably cellular; loose fascicles of spindle cells
Pale eosinophilic cytoplasm
Ovoid nuclei with mild pleomorphism; inconspicuous mitotic activity
Myxoid-collagenous stroma; Ectatic-hyalinized blood vessels
IHC: S100, SOX10, epithelial membrane antigen
RNA-seq: SS18::SSX2 gene fusion
Fascicles of spindle cells
Eosinophilic cytoplasm
Ovoid nuclei with fine chromatin and inconspicuous nucleoli; occasional mitotic activity
Wiry collagen interspersed between the cells; dystrophic calcification
IHC: AE1/AE3, SATB2
RNA-seq: SS18::SSX1 gene fusion
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
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
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
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
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
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
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
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
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
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
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
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
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