[Prostate carcinoma and syndrome of inappropriate antidiuretic hormone secretion]

Prostate cancer is an extremely rare cause of syndrome of inappropriate antidiuretic hormone (SIADH) secretion. These tend to be aggressive tumors and SIADH can carry serious clinical consequences. A 64 years old patient was diagnosed with Gleason 4+3: 7 prostate adenocarcinoma in December 2014 and received hormonal blockade therapy. By March 2015 he was admitted for symptomatic hyponatremia and SIADH secretion was diagnosed, with no other probable cause than prostate cancer. He suffered a rapid progression of his oncologic disease, surprisingly with PSA in normal range, and died in the short term. There is great clinical and histopathological variability in the cases reported in the literature of association of prostate carcinoma and SIADH. However, they all agree on the aggressiveness of these tumors. This characteristic is present in tumors that have neuroendocrine features. They are frequently resistant to hormonal treatment and may present with paraneoplastic syndromes such as SIADH. The profile of its molecular alterations is under study for the development of target therapies. The association of prostate adenocarcinoma and SIADH is very uncommon and could involve neuroendocrine differentiation. For this reason, it is essential to perform a new biopsy of the tumor or its metastases at the progressive disease in order to conduct an appropriate treatment according to its morphological, immunohistochemical and, in the future, molecular characteristics.