A neuroendocrine carcinoma of the prostate gland with unfavorable prognosis, composed of small cells containing neurosecretory granules. Approximately half of the cases show a mixture of small cells and adenocarcinoma cells. The disease is prostate small cell carcinoma (Monarch Disease Ontology id MONDO_0006390). Also known as: Oat cell carcinoma of prostate, Oat cell carcinoma of the prostate, prostate Oat cell carcinoma, prostate gland small cell carcinoma, prostate oat cell carcinoma, prostate small cell NEC, prostate small cell neuroendocrine carcinoma, small cell carcinoma of prostate.