Urothelial Carcinoma With Divergent Glandular Differentiation.

Divergent differentiation in urothelial carcinoma is a challenging phenomenon that often makes the proper histopathological diagnosis a challenge. Conventional foci are often scarce in this subclass of urothelial carcinoma, and even if proper grossing and slide processing is performed, inexperienced pathologists can miss them. Furthermore, divergent differentiation in urothelial carcinoma is important to be recognized as such not only for the true diagnosis to be established and hence not increase the statistical incidence of rare neoplasms but also as divergent differentiation is one of the key factors in defining urothelial carcinomas as high-grade and hence crucial for proper patient management and treatment. Herein, we report a histopathological case of a male patient in his 60s who had been diagnosed with a high-grade urothelial carcinoma with submucosal involvement one year prior. Due to symptom recurrence, a follow-up endoscopy and resection of suspicious areas were performed to check for disease recurrence. Histopathology revealed a malignant neoplasm with histomorphological features of predominantly colonic-type adenocarcinoma and only a few areas with urothelial papillary morphology. Hence, divergent differentiation of the neoplasm was noted. Other than not falsely increasing the incidence of rare bladder malignancies, proper recognition of urothelial divergent differentiation is also important for excluding metastatic lesions to the bladder, as most of the diverging types of differentiation are common in neighboring organs or in tumor types that have pronounced metastatic potential.