The frequent correlation of small cell carcinoma of the urinary bladder with urothelial carcinoma is suggesting that small cell carcinoma may originate from urothelial stem cell rather than a specific neuroendocrine precursor cell [12] Immunohistochemical stains show high positivity for Chromogranin, Synaptophysin, neuron-specific enolase, Keratin7, and epithelial membrane antigen (EMA).One of the differential diagnosis of small cell carcinoma is metastasis from another site. The gene discussed is MUC1; the disease is urinary bladder small cell neuroendocrine carcinoma.