Summary

We present a very rare case of de novo large cell neuroendocrine carcinoma (LCNEC) of the prostate in an 84-year-old man on a background of high grade, superficially invasive transitional cell carcinoma of the bladder. Pure LCNEC of the prostate is extremely rare. Most LCNEC of the prostate are thought to originate by clonal progression under the selection pressure of therapy and refractory to long-term hormonal treatment for adenocarcinoma of the prostate. De novo LCNEC is only described in case reports and is thought to develop via direct malignant transformation. Limited data in the English literature makes it difficult to accurately predict the prognosis of LCNEC of the prostate. However, current evidence suggesting that increasing neuroendocrine differentiation in prostate adenocarcinoma is associated with a higher stage, high-grade disease and a worse prognosis.