Sarcomatoid Urothelial Carcinoma With Myxoid Stroma: A Case Report and Diagnostic Approach.

Bladder cancer is the seventh most common cancer in the world. Urothelial carcinoma is the most common type of bladder cancer. Other subtypes like squamous cell carcinoma and adenocarcinoma are less common. Urothelial carcinoma has a propensity for divergent differentiation. Sarcomatoid carcinoma is one of the variants of urothelial carcinoma. It is an aggressive tumor that presents at an advanced stage and has a poorer prognosis than conventional urothelial carcinoma. Therefore, identifying this variant histology is important clinically. The sarcomatoid component in sarcomatoid carcinoma can be spindle cell (not otherwise specified), myxoid, pseudoangiosarcomatous, and undifferentiated sarcoma like. Myxoid stroma in sarcomatoid urothelial carcinoma has been described but reported very rarely. We present a case of sarcomatoid urothelial carcinoma with myxoid stroma along with a review of the diagnostic approach to myxoid spindle cell lesions of the urinary bladder.