Small cell carcinoma of the urinary bladder: changing trends in the current literature.

Background Extrapulmonary small cell carcinoma (SmCC), also known as oat cell carcinoma or small cell neuroendocrine carcinoma, is characterized by an aggressive clinical course with early metastasis pattern and a short life expectancy. So far, there is no prospective, data-based case-control study due to its low incidence. The purpose of this paper is to discuss the epidemiology, morphopathology, clinical characteristics, differential diagnosis and treatment of bladder SmCC in the light of the literature. Scope PubMed and American Society of Clinical Oncology Meeting abstracts were searched according to the following keywords: 'extrapulmonary SmCC', 'bladder cancer', and 'therapeutic approach'. The last search was performed on 1 October 2015. Some additional papers were determined by reviewing references of the appropriate articles. Most of the data regarding small cell carcinoma of the urinary bladder (SmCCB) were found to be based on the retrospective trials. Findings Bladder SmCC is more frequent in men and usually appears in the seventh to eighth decades. Macroscopic hematuria is the most common clinical symptom. The diagnosis of SmCCB is performed based on the same criteria determined by the WHO classification for the diagnosis of small cell lung carcinoma (SCLC). Prognosis is closely correlated with the stage at presentation. Although the prognosis of the disease is poor, a long survival can be achieved particularly by radical surgery following neoadjuvant chemotherapy in patients with early stage tumors. Cystectomy is still the current standard local treatment. However, cystectomy alone is not sufficient. Chemotherapy and definitive radiotherapy should be preferred for limited disease in patients who are not candidate for surgery. Conclusion Considering the poor prognosis of the disease, further studies are needed to determine the optimal treatment options and new molecular markers in the way of early diagnosis and favorable outcomes. Prospective, multicenter, randomized studies are required to evaluate the role of neoadjuvant chemotherapy followed either by surgery or radiotherapy.