Diagnostic and Ethical Challenges in a Rare Case of Retroperitoneal Carcinosarcoma During Pregnancy—A Case Report and Literature Review

<b>Background and Clinical Significance:</b> Carcinosarcomas are highly aggressive tumors with both carcinomatous and sarcomatous components, typically arising from the female genital tract. Primary retroperitoneal carcinosarcomas are extremely rare, and their occurrence during pregnancy presents major clinical and ethical challenges. <b>Case Presentation:</b> We report a case of a 24-year-old primigravida diagnosed with a large encapsulated retroperitoneal mass at 12 weeks of pregnancy, initially presenting with abdominal pain. The patient declined medical advice for pregnancy termination and chose to continue despite oncological risks. A multidisciplinary team planned delayed surgery after delivery. At 34 weeks, a cesarean section resulted in a healthy newborn, but surgical exploration revealed an inoperable, invasive tumor. The patient died two days later from postoperative complications. Autopsy confirmed widespread tumor invasion and lung metastases consistent with primary retroperitoneal carcinosarcoma. <b>Conclusions:</b> This case highlights the challenges of managing aggressive malignancies during pregnancy, emphasizing early diagnosis, multidisciplinary care, and ethical decision-making while respecting patient autonomy.