Clinically Occult Cecal Metastasis From Prostate Adenocarcinoma Detected by 18F-PSMA Positron Emission Tomography at Biochemical Recurrence

We present a patient with biochemical recurrence after salvage radiation and combined androgen deprivation therapy with abiraterone who underwent 18 F-PSMA PET/CT for a rapidly rising prostate-specific antigen (PSA). The scan revealed an intense prostate-specific membrane antigen (PSMA)-avid focus in the cecum without an apparent CT correlate. Colonoscopy identified a smooth, 2 cm nonobstructing cecal mass, and biopsy confirmed metastatic prostate adenocarcinoma by morphology and immunohistochemistry. This case demonstrates 18 F-PSMA PET/CT detection at a low PSA level of a clinically occult metastatic lesion involving the cecum, an exceptionally rare site for prostate cancer spread. Colonoscopy and biopsy confirmation of atypical PSMA-avid gastrointestinal lesions remain essential, as physiologic colonic uptake, PSMA-avid diverticula, and PSMA-expressing primary colorectal cancers are well-documented mimickers.