Adenomyofibroma of the endometrium with skeletal muscle differentiation

A case of adenomyofibroma with skeletal muscle differentiation is described . A 55-year-old asymptomatic woman had atypical glandular cells of undeterm ined significance on a routine Papanicolaou smear. The endometrial biopsy r evealed fragments composed of benign endometrial glands and myofibromatous stroma with foci of skeletal muscle differentiation. The stroma exhibited f ocal mild cytologic atypia and hypercellularity without periglandular cuffi ng or mitoses. Electron microscopy and immunohistochemical staining for myo globin confirmed the skeletal muscle differentiation. A diagnosis of low-gr ade adenosarcoma with heterologous differentiation was made in the biopsy s pecimen based on the atypical struma, the skeletal muscle differentiation, and previous observations that adenosarcomas may contain bland areas indist inguishable from an adenofibroma. The patient underwent hysterectomy: bilat eral salpingo-oophorectomy, and pelvic lymphadenectomy. The hysterectomy sp ecimen revealed small foci of residual turner. In light of these findings t he diagnosis was revised to adenomyofibroma with skeletal muscle differenti ation. Uterine adenolnyofibroma with skeletal muscle differentiation should be distinguished from a low-grade adenosarcoma in an endometrial biopsy.