Fallopian Tube Carcinosarcoma With Intrauterine Fluid Accumulation: MRI Findings, Diagnostic Challenges, and Long-Term Survival

Fallopian tube carcinosarcomas are extremely rare biphasic malignancies with nonspecific clinical and imaging features, posing significant diagnostic challenges. We report a case of a heterologous carcinosarcoma originating from the fimbriated end of the fallopian tube, presenting as a right adnexal mass with intrauterine fluid accumulation in the absence of hydrosalpinx. Magnetic resonance imaging demonstrated heterogeneous high signal intensity on T2-weighted imaging, low signal intensity on T1-weighted imaging, and patchy enhancement on both early- and delayed-phase contrast-enhanced sequences. The tumor was surgically resected, and it was histologically diagnosed as a heterologous carcinosarcoma with chondrosarcomatous components. The patient underwent a two-stage surgery with dose-dense chemotherapy and achieved long-term survival, remaining recurrence-free for over 11 years. This case highlights the importance of considering fallopian tube carcinosarcoma in the differential diagnosis of adnexal tumors and demonstrates the potential favorable outcomes with timely intervention and appropriate treatment.