Stage IVB ovarian carcinosarcoma in BRCA wild-type patients: two case reports of unexpected long-term remission

Background: Ovarian carcinosarcoma (OCS), also known as malignant mixed Müllerian tumor, is a rare and highly aggressive subtype of epithelial ovarian cancer, accounting for less than 4% of all cases. It typically presents at advanced stages and is associated with dismal outcomes, with a five-year survival rate below 30%. Despite improvements in cytoreductive surgery and systemic therapies, long-term survival in stage IV disease remains exceedingly uncommon. Case presentation: We report two exceptional cases of stage IVB Müllerian carcinosarcoma occurring in BRCA wild-type postmenopausal women who achieved prolonged complete remission exceeding five years after multimodal management. The first patient, aged 61, presented with bilateral adnexal masses and a solitary pulmonary metastasis. She underwent primary cytoreductive surgery including hysterectomy, bilateral adnexectomy, lymphadenectomy, appendicectomy, and omentectomy, followed by six cycles of platinum-taxane chemotherapy. Residual pulmonary disease was later removed via video-assisted thoracoscopic lobectomy, confirming metastatic OCS. Post-recurrence, she received off-label maintenance with tamoxifen 20 mg daily for five years and remains disease-free at 70 months. The second patient, aged 70, presented with a pelvic mass invading the recto-sigmoid wall and a synchronous hepatic metastasis. She underwent extensive cytoreductive surgery including hysterectomy, en-bloc rectal resection, lymphadenectomy, cholecystectomy, and liver wedge resection, achieving complete macroscopic cytoreduction. Histology confirmed a Müllerian carcinosarcoma with a predominant endometrioid component. Postoperative chemotherapy with carboplatin-paclitaxel was followed by maintenance niraparib 100 mg twice daily for three years. She remains in complete remission at 60 months. Discussion: Both patients demonstrate durable disease control in the absence of germline or somatic BRCA mutations, suggesting that long-term remission may be achievable even in BRCA-wild-type OCS through optimal surgery and individualized maintenance approaches. Tamoxifen, rarely employed in this setting, may have provided estrogen-receptor-mediated tumor suppression in the first case, while the second case highlights potential activity of PARP inhibition beyond BRCA mutation carriers. Conclusion: These two reports challenge the long-held perception of uniformly poor outcomes in metastatic ovarian carcinosarcoma. Complete cytoreductive surgery combined with tailored systemic and maintenance therapies can achieve sustained remission even in advanced-stage BRCA-wild-type patients. Broader molecular profiling and international collaboration are essential to refine management strategies for this rare and aggressive malignancy.