Small cell carcinoma of the bladder is a rare, aggressive, poorly differentiated neuroendocrine neoplasm that is similar to small cell carcinoma of the lung in clinical behavior. Although small cell carcinoma is classified as a discrete entity, molecular studies have indicated that small cell carcinoma and urothelial cancer are derived from the same clonal population . Bladder small cell carcinoma is frequently found in conjunction with other histologic forms of bladder cancer. As an example, in a series of 66 cases from one institution, 44 (68 percent) had other tumor types present, including elements of urothelial cancer in 38 cases (58 percent of the total series) . Similarly, a series of 51 cases of small cell carcinoma at another institution reported that elements of urothelial carcinoma, adenocarcinoma, and squamous cell carcinoma were seen in 70, 8, and 10 percent of the cases, respectively .
Small cell carcinoma of the bladder will be reviewed here. Extrapulmonary small cell carcinomas at other sites are discussed separately. (See "Extrapulmonary small cell cancer".)
Between 1991 and 2005, the incidence of small cell carcinoma (SCC) of the bladder increased significantly from 0.05 to 0.14 cases per 100,000 population, but still represents less than one percent of all bladder tumors [4,5]. There are roughly 500 new cases of SCC of the bladder annually. In an analysis of demographics for patients with SCC using the Surveillance, Epidemiology and End-Results (SEER) database, the following was noted :
- Men are affected more commonly than women (76 versus 24 percent)
- Whites are affected more commonly than non-whites (91 versus 9 percent).
- The median age of diagnosis of SCC is 73 years.
- Median overall survival was 11 months, but outcomes varied substantially based on the presence or absence of distant metastases at the time of diagnosis.
A past history of smoking has also been associated with SCC of the bladder .