Small cell carcinoma of the bladder (ORPHA:284400)
Small cell carcinoma of the bladder (SCCB) is a very rare, poorly differentiated neuroendocrine epithelial bladder tumor characterized clinically by hematuria and/or dysuria and a highly aggressive course.
Epidemiology
SCCB is extremely rare with an annual incidence of less than 1-9/1,000,000. Since 1980, fewer than 1,500 cases have been identified. The demographic profile of SCCB is similar to that of patients with bladder transitional cell carcinoma (TCC). The majority of patients are male, with a mean sex ratio of 5:1, and a range between 1:1 to 16:1. The vast majority of cases were reported in the Caucasian population.
Clinical description
Most knowledge on SCCB is based on retrospective investigations and on a few prospective studies. Mean age at diagnosis is 67 years (range 32 to 91 years). The clinical features of SCCB are similar to those of bladder TCC and reflect the presence of a tumoral mass. The main symptom is gross hematuria (63 to 88% of cases) with dysuria as the second most common symptom. Urinary obstruction, abdominal pain, urinary tract infection and weigh loss are occasionally present. SCCB often occurs with other types of carcinoma and is frequently found combined with other histological forms of bladder cancer: TCC, adenocarcinoma and squamous cell carcinoma. SCCB is generally believed to have a high metastatic potential. Rare cases of paraneoplastic syndromes such as ectopic ACTH secretion and hypercalcemia have also been reported.
Etiology
The etiology of the disease is unknown but a multipotent stem cell anomaly is thought to be a likely mechanism. A history of smoking is found in 65% to 79% of cases.
Diagnostic methods
Histology and immunohistochemistry show a tumor that is indistinguishable from small cell lung cancer (SCLC; see this term). Diagnosis of SCCB relies mainly on histopathological data obtained by cystoscopy and transurethral resection of the bladder tumor. Immunochemistry staining is useful in establishing the diagnosis. Light microscopy reveals packed cells having scant cytoplasm containing few organelles. Tumors are composed of nests of small round malignant cells with pyknotic round to oval nuclei and evenly dispersed ''salt and pepper chromatin''. More than 95% of SCCB cases are diagnosed at muscle invasive stage T2 or later.
Differential diagnosis
The differential diagnosis includes direct invasion of the bladder by SCC of the prostate, metastatic SCC from another source, usually the lung, and primary lymphomas of the bladder.
Management and treatment
The staging system used is the TNM-staging of bladder transitional cell carcinoma. Treatment is extrapolated from that of SCLC. However, many patients with SCCB undergo radical resection which is rarely performed in SCLC. Patients with surgically resectable disease should be managed with multimodal therapy associating chemotherapy, surgery and/or radiotherapy. Neoadjuvant chemotherapy using 4 chemotherapy cycles followed by radical cystectomy is the most effective therapeutic sequence. Patients with unresectable disease should be managed with palliative chemotherapy based on neuroendocrine-type regimens comprising a platinum drug (cisplatin in fit patients). Prophylactic cranial irradiation should be considered in stages III/IV bladder SCC.
Prognosis
The prognosis of the disease is poor mainly in the case of pure small cell carcinoma.

                            Last update: 
                            April 2012


                            - Expert reviewer(s): 
                            Dr NABIL ISMAILI