Small cell metastatic prostate cancer with ectopic adrenocorticotropic hormone hypersecretion.

Small cell prostate cancer (SCPC) is a rare entity with an incidence of 0.5-2% of all prostate carcinomas. SCPC is characterized by low prostate specific antigen (PSA) levels, lack of response to androgen deprivation therapy and distal dissemination with visceral metastases at diagnosis in 70% of patients. Moreover, it can present as paraneoplastic syndromes including Cushing's syndrome or hypercalcemia, which worsens prognosis. We report a case of 65-year-old male attending the emergency department with hyperaldosteronism clinic. After completing the study, locally advanced SCPC with multiple metastatic adenopathies is diagnosed. It shows low PSA levels, high adrenocorticotropic hormone (ACTH) levels and an immunohistochemistry (IHC) showing positivity for CD56 and synaptophysin. He presented a poor evolution of hypercortisolemia in the context of a paraneoplastic syndrome with ACTH hypersecretion. SCPC is a challenge in its diagnosis and treatment due to few reports in the literature. As this tumor can go unnoticed, a high diagnostic suspicion is necessary, being the biopsy the gold standard for its confirmation. Pathological study with IHC analysis, including neuroendocrine (NE) markers, are essential for its diagnosis. Despite systemic chemotherapy, prognosis is poor because of local and distant aggressiveness. Hence, the aim of treatment is to control cancer trying to offer a good quality of life. New lines of treatment are being investigated.