Spindle cell fascicles
Pale amphophilic cytoplasm
Monomorphic ovoid nuclei with vesicular chromatin and small nucleoli; inconspicuous mitotic activity
Mild lymphocytic infiltrate
IHC: ERG, keratin (AE1/AE3)
RNA-seq: ACTB::FOSB gene fusion
PMID: 30256258
Spindle cell fascicles
Pale amphophilic cytoplasm
Monomorphic ovoid nuclei with vesicular chromatin and small nucleoli; inconspicuous mitotic activity
Mild lymphocytic infiltrate
RNA-seq: SERPINE1::FOSB gene fusion
PMID: 24374978
Multifocal; fascicles of spindle-stellate cells
Eosinophilic cytoplasm
Hyperchromatic ovoid nuclei with mild pleomorphism; inconspicuous mitotic activity
Loose fibrous stroma
IHC: CD31, ERG, keratin (AE1/AE3)
RNA-seq: MED15::FOSB gene fusion*
* To date unreported in literature
Multifocal; fascicles of spindle-stellate cells
Pale eosinophilic cytoplasm
Elongated ovoid nuclei with vesicular chromatin and small nucleoli; inconspicuous mitotic activity
Intervening myxoid stroma
RNA-seq: SERPINE1::FOSB gene fusion
PMID: 24374978