Prostatic Malakoplakia as a Mimic of Prostate Cancer Progression.

Prostatic malakoplakia is a rare chronic inflammatory condition that can present as a cancer mimic and can co-occur with prostate adenocarcinoma. Typically, patients with prostate adenocarcinoma who present with evidence of disease progression while on androgen deprivation therapy (ADT) and a low prostate-specific antigen (PSA) level raise concern for transformation to small cell neuroendocrine carcinoma (SCNEC) of the prostate. A 67-year-old man with known locally advanced prostate adenocarcinoma was admitted with functional decline, radiographic tumor growth, and a low PSA. A repeat prostate biopsy was obtained to assess for transformation to SCNEC, but instead showed concurrent malakoplakia with his stable adenocarcinoma. With antibiotics, his peri-prostatic mass decreased in size, and he experienced an improvement in his functional status, allowing him to resume his ADT. Recurrent urinary tract infections, solid tumors, and immunosuppression are all risk factors for the development of prostatic malakoplakia, which is diagnosed pathologically from biopsy or after prostatectomy. Treatment is either long-term antibiotics or surgical resection. Prostatic malakoplakia should be considered as a mimic of disease progression in patients who have evidence of cancer progression despite a lower-than-expected PSA.