Small-cell bladder cancer: literature review

Worldwide, bladder cancer is the 7^th most common cancer type in men and 11^th in both sexes. The standardized by age incidence is 9.0 cases per 100.000 people among men and 2.2 cases per 100.000 people among women.

The most common (>90 %) histological form of malignant epithelial tumors of the bladder is transitional cell carcinoma. Transitional cell carcinoma with squamous cell, glandular, or trophoblastic differentiation is rare. Squamous cell carcinoma comprises about 5 % of malignant epithelial bladder tumors, adenocarcinomas from 0.5 to 2.0 %. Small-cell and spindle-cell carcinomas are exceptionally rare (<0.5 %). Primary small-cell, or neuroendocrine, carcinoma is a very rare disease with incidence of <0.5 % of all bladder tumors. Presumably, small-cell carcinoma of the bladder (SCCB) is similar to small-cell carcinoma of the lung and consists of a population of a relatively homogenous cells with scant cytoplasm and hyperchromatic nuclei; extensive necrosis is also common. Histogenesis of SCCB is unknown, but there are 2 hypotheses on development of cancerous cells: from rare neuroendocrine cells and multipotent stem cells of the bladder.

Prognosis is poor for most patients: in the report by I. Trias et al., median survival was less than 1 year, long-term survival for 5 or more years was extremely rare. In more than a half of patients, metastatic lesions of the regional lymph nodes, liver, or bones were observed during diagnosis.

In the Russian literature, the problem of SCCB remains insufficiently investigated due to low incidence of this morphological type. Treatment is mostly administered empirically.

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