Literature review of small cell carcinoma of the urinary bladder

Abstract

Small cell carcinoma of the urinary bladder is a rare tumour that resembles small cell carcinoma in the lung and elsewhere. Because of its rarity, practitioners may not be familiar with the biological behaviour of this tumour. The aim of this article is to review the literature on small cell carcinoma of the urinary bladder. Various internet search engines were used to explore the literature on small cell carcinoma of the urinary bladder including Google, Google Scholar, UpToDate, Pub Med and Educus. About 42 references were selected as the basis for the literature review. Small cell carcinoma of the urinary bladder is an aggressive tumour that typically presents with advanced or disseminated disease. This is a rare disease, accounting for only 0.5–1.0% of all bladder malignancies. Affected individuals show no age, sex or clinical differences from those with the typical type of urothelial carcinoma. Some cases of small cell carcinoma of the urinary bladder arise from urothelial carcinoma in situ while others arise from totipotent stem cells in the submucosa. The tumours are usually large polypoid masses that can occur anywhere in the bladder. Microscopically, the tumours appear as loosely cohesive sheets, or nests, of small to intermediate-sized cells with minimal cytoplasm, hyperchromatic nuclei, stippled or coarsely granular chromatin, indistinct nucleoli and no nuclear overlapping. Mitotic activity and necrosis are common and the tumours may co-exist with other forms of in situ, or invasive, carcinoma. Radical cystectomy is the main treatment for small cell carcinoma of the urinary bladder, unless metastatic disease is present, followed by systemic treatment. Response to chemotherapy is good, similar to treatment for small cell carcinoma of the lung, but the overall prognosis remains poor. There is no consensus regarding treatment of small cell carcinoma of the urinary bladder although general recommendations for the approach to treatment of this aggressive disease have been suggested.