Small cell carcinoma of the bladder: the characteristics of molecular alterations, treatment, and follow-up.

Small cell carcinoma of the bladder (SCCB) is a rare disease associated with high invasiveness and mortality. Histologically, SCCB is difficult to distinguish from small cell lung cancer (SCLC); however, it shares more similar molecular alterations with urothelial carcinoma (UC). As a result, now, the widely accepted theory about the cells of origin is that SCCB and UC probably have a common clone origin. Even the former probably comes from a preexisting UC. At present, given its rarity, early diagnoses, treatments, and follow-ups are not well established, which are vital to patients with SCCB. Inspirationally, in recent years, with the development of molecular diagnostic methods, molecular alterations of SCCB have been understood partially, which are propitious to excavate new potential therapeutic strategies and establish sound follow-ups. Therefore, the future will be light for patients with SCCB.