ABSTRACT
Endometrial stromal sarcoma (ESS) has a wide histopathological spectrum with CD10 as its diagnostic marker. Recently, few non-conventional ESSs have been identifi ed that lack diffuse CD10 expression. A 46-year-old, perimenopausal lady referred to us with history of vaginal bleeding. On clinical examination and radiological imaging, a polypoid endometrial tumor was identifi ed. Hysterectomy revealed a multinodular tumor in the myometrium. Microscopically, the tumor composed of rather banal oval to spindle-shaped cells in a fi bromyxoid stroma. Focal areas displayed compact cellular arrangement, unassociated with signifi cant mitoses and necrosis. Immunohistochemically, tumor cells were focally positive for CD10, estrogen receptor, progesterone receptor, p16INK4 and were diffusely positive for cyclinD1. Diagnosis of cyclinD1 and p16INK4 positive ESS was offered. This case highlights the value of additional IHC markers, especially cyclinD1 and p16INK4 in order to identify certain ESSs that lack diffuse CD10 immunoexpression; are invariably misdiagnosed as undifferentiated sarcomas, but actually form a relatively more aggressive subset of ESSs.