Endometrial stromal sarcoma presenting as extrauterine metastases: A morphologic and immunohistochemical approach to diagnosis

A case of endometrial stromal sarcoma that initially presented as an umbilical mass 5 years before and as a lung lesion 8 months before the primary tumor was detected in the uterus is reported. The morphologic features and immunohistochemical profile of the two initial extrauterine lesions suggested metastases from a primary endometrial stromal sarcoma of the uterus, which was confirmed by subsequent endometrial curettage. The tumors in all three locations were characterized histologically by small to medium-sized uniform cells with fewer than 10 mitoses per 10 high-power fields and distinct arterial vasculature that resembled the spiral arteries of the normal endometrium. Both the endometrial and umbilical tumors were immunoreactive for estrogen and progesterone receptors but showed no immunoreactivity for cytokeratin. Additionally, the tumor cells of the umbilical mass showed no immunoreactivity for S- 100 protein, HMB-45, smooth- muscle actin, or desmin. Endometrial stromal sarcomas are usually confined to the uterus at the time of diagnosis. When they present initially as an extrauterine metastasis, diagnostic difficulties may arise. A recognition of the morphologic features, together with the immunoreactivity pattern, is needed in evaluating endometrial stromal sarcomas that present as extrauterine metastases.