Primary Ewing's sarcoma of vulva: a case report and a review of the literature.

Ewing sarcomas/peripheral primitive neuroectodermal tumors (ES/pPNET) are extremely rare in the vulva. A review of the literature reveals only 14 previously reported possible cases. Here we reported a case of primary extraskeletal Ewing's sarcoma (EES) of the vulva in a 37-year-old woman. Characteristic histologic features of ES/pPNET were present in this case, including a monomorphic population of small round blue cells with cytoplasmic glycogen confirmed by periodic acid-Schiff, membrane staining with CD99 and nuclear staining with FLI-1. After surgery, the patient was found to have pulmonary metastasis and then received six cycles of polychemotherapy. She is still alive with stable disease after 1 year of follow up. Our findings underline the crucial role of immunohistochemical techniques in the differential diagnosis of small round cell tumors in these unusual locations. We also give a summary about the clinical and pathological features of the primary ES/pPNET in the vulva reported previously in the literature.