Diffuse Uptake in Small Cell Prostate Cancer With Penile Metastasis on 18F-FDG PET/CT

A 77-year-old man, initially suspected of benign prostatic hyperplasia, underwent transurethral resection of the prostate 1 month ago. He presented with persistent urinary retention for 2 weeks. MRI revealed a soft tissue mass in the prostate and penile cavernous body with hyperintensity on T2WI, diffusion-weighted imaging (DWI), and hypointensity on apparent diffusion coefficient (ADC), with enhancement showing heterogeneous linear and cord-like patterns on contrast-enhanced T1WI. 18 F-FDG PET/CT demonstrated diffuse FDG uptake in the prostate, liver, and penile cavernous body. Biopsy confirmed small cell prostate cancer (SCPC). This case highlights the utility of FDG PET/CT in detecting both primary and metastatic lesions of SCPC, particularly in detecting rare penile involvement.