Small cell carcinoma of the urinary bladder: a rare tumor with propensity for hepatic involvement

Small cell (neuroendocrine) carcinoma of the bladder is a rare entity, accounting for less than 1% of all bladder tumors. The authors report 2 new cases of the disease, both presenting with liver metastasis. In the first case, small cell carcinoma occurred in an 85-year-old woman as tumor recurrence of previous micropapillary carcinoma and urothelial carcinoma in situ, illustrating the common coexistence with conventional urothelial carcinoma. In the second case of a 58-year-old man, non-small cell tumor components were not observed. Accurate diagnosis of small cell carcinoma may be challenging. A panel of different antibodies, including neuron-specific enolase, chromogranin A, synaptophysin and CD56 (neural cell adhesion molecule) is recommended. In conclusion, small cell carcinoma represents a rare and aggressive form of bladder malignancy. As illustrated by the 2 cases and according to the literature review, the tumor shows a so far underrecognized propensity for hepatic involvement.