Fig. 1

Microscopic findings of malignant uterine PEComa (case 1, a–d). Punch biopsy from vagina (a, b); section showing atypical epithelioid tumor cells with marked necrosis (a, original magnification ×100). Immunostaining was negative for HMB45 (b, ×100). Tumor mass obtained by hysterectomy (c, d); section revealing epithelioid tumor cells with cytologic atypia and high mitotic activity (arrow) (c, ×200). The tumor cells showed patchy HMB45 expression by immunostaining (d, ×200). Microscopic findings of uterine mass (case 2, e, f). The tumor showed local infiltration into adjacent uterine smooth muscle (e, original magnification ×40) and predominantly benign-looking epithelioid tumor cells (f, ×400)