Rare Prostatic Metastasis from Rectal Cancer Detected by ¹⁸ F-FDG PET/CT

Abstract

Colorectal cancer (CRC) most commonly metastasizes to the liver, lungs, peritoneum, and bones. Prostatic metastasis is exceptionally rare, with only a handful of cases reported worldwide. It typically arises in the context of advanced disease and widespread dissemination, often portending a poor prognosis. Early recognition of such atypical sites is essential for guiding therapy. 18 F-fluorodeoxyglucose positron emission tomography/computed tomography ( 18 F-FDG PET/CT) enables whole-body metabolic imaging and can detect hypermetabolic lesions in unexpected locations, but histo-pathological confirmation with immunohistochemistry remains indispensable for differentiating metastatic CRC from primary prostatic or bladder adenocarcinoma. We describe the rare case of a patient with a history of rectal moderately differentiated adenocarcinoma who developed lower uri-nary tract symptoms during the follow-up. 18 F-FDG PET/CT revealed a solitary hypermetabolic focus within the prostate. Subsequent biopsy with immunohistochemical profiling confirmedmetastatic rectal adenocarcinoma. The patient commenced systemic chemotherapy, achieving partial symptom relief and radiological disease stabilization at a 3-month follow-up, without new metastatic foci. This case highlights the diagnostic value of PET/CT and pathology correlation in identifying exceptionally rare metastatic presentations of CRC.