Ovarian carcinosarcoma typically comprises high‐grade carcinoma and sarcoma components. We report a case of a woman in her 40s with endometriosis‐associated ovarian carcinosarcoma exhibiting an unusual presentation of well‐differentiated adenocarcinoma and rhabdomyosarcoma. The patient underwent bilateral salpingo‐oophorectomy and hysterectomy for tumors in both ovaries. Histologically, with a background of endometriosis, the epithelial component exhibited features of a borderline tumor with an intraepithelial carcinoma composed of Müllerian‐type epithelium in both ovaries. In the left ovary, a very minor area of clear cell carcinoma (less than 5%) was identified. In contrast, the mesenchymal component was a well‐differentiated rhabdomyosarcoma resembling fetal rhabdomyoma, constituting more than 60% of the left ovarian tumor. One year later, pulmonary metastases of the sarcomatous component were detected. Molecular analysis using next‐generation sequencing identified PIK3CA H1047R (c.3140A > G) and CSF1R (c.∗1841TG > GA) in both the epithelial and mesenchymal components, indicating a clonal origin and supporting a diagnosis of primary ovarian carcinosarcoma. The patient died 29 months after surgery despite receiving platinum‐based chemotherapy. This report highlights the challenges of diagnosing rare ovarian carcinosarcomas arising in endometriosis and with unusually low‐grade histology, and it emphasizes the need for comprehensive pathological assessment, including molecular analysis, for accurate diagnosis and optimal management.
Narusawa et al. (Thu,) studied this question.