Mixed carcinoma transdifferentiation of bladder urothelial carcinoma after chemotherapy: A case report.

Both small cell carcinoma (SCC) and sarcomatoid carcinoma are rare malignancies of the bladder, with their simultaneous presence being exceedingly rare. The present study reports the case of a patient who underwent multiple transurethral resections for bladder tumors, with initial diagnoses consistently indicating urothelial carcinoma (UC). However, the pathology from the fourth surgery revealed a complex presentation of mixed bladder cancer, primarily characterized by sarcomatoid carcinoma, but also including SCC and traditional UC. After the operation, it was recommended that the patient should receive neoadjuvant chemotherapy combined with radical cystectomy as a treatment strategy, but due to the poor physical condition of the patient, this was refused; therefore, the patient was instead followed up closely for a long period. However, the patient died of multiple organ failure 9 months after the operation. After conducting an extensive review of the literature, it was concluded that UC undergoing transdifferentiation into SCC of the bladder and sarcomatoid carcinoma following chemotherapy is well founded. Immunotherapy represents a promising new treatment avenue for these highly malignant and advanced-stage tumors, offering substantial potential for research. Additionally, studies investigating the mechanisms underlying promising therapeutic regimens need to be conducted in greater depth in the near future.