Small cell carcinoma of the bladder presenting with paraneoplastic syndrome of inappropriate antidiuretic hormone.

Small cell carcinoma (SCC) of the bladder is a rare malignancy, representing less than 1% of bladder cancers diagnosed annually in the USA. In contrast to SCC of the lung, paraneoplastic syndromes are rarely documented in cases of extrapulmonary SCCs, particularly those of genitourinary origin. We present a case of SCC of the bladder presenting with paraneoplastic syndrome of inappropriate antidiuretic hormone, which resolved after treatment with sequential chemoradiation. © BMJ Publishing Group Limited 2019. No commercial re-use. See rights and permissions. Published by BMJ.