Composite tumor consisting of dermatofibrosarcoma protuberans and giant cell fibroblastoma associated with intratumoral endometriosis. Report of a case.

We present a unique case of composite skin tumor of the vulva consisting of dermatofibrosarcoma protuberans (DFSP) and giant cell fibroblastoma (GCF) with an intratumoral focus of endometriosis. A 31-year-old female with a 10-year-history of a recurring subcutaneous tumor in the vulvar area underwent excision of the seventh recurrence of the tumor. Microscopic examination revealed a composite fibrohistiocytic tumor consisting of DFSP and GCF. Additionally, a focus of endometriosis within the tumor tissue was found. Malignant transformation of extragonadal endometriosis has already been described; we present, however, the occurrence of a focus of endometriosis within the tissue of a hormonally independent soft tissue tumor. There is a possible link to the occurrence of cutaneous endometriosis at previous surgery sites and in the scars. The presence of endometriosis within the soft tissue tumor represents, to the best of our knowledge, a previously undescribed collision phenomenon.