An Extremely Rare Metastatic Prostate Tumor From Rectal Cancer With Characteristic MRI Findings Due to Necrosis

Colorectal carcinomas rarely metastasize to the prostate. Early detection of metastatic prostate tumors can lead to possible cure with less invasive treatment. A 71-year-old man was diagnosed with rectal cancer and underwent surgery for it. The postoperative pathological study showed atypical cells growing mainly cribriform and some large necrosis in the tubule-forming structures. After favorable control of the recurrent lesion for 30 months, the MRI showed the right lobe tumor with low signals on diffusion-weighted images. CT clarified the enlargement of the right lobe mass in the prostate four years after the surgery. The patient, therefore, underwent total pelvic exenteration, including prostatectomy. The postoperative pathological study showed metastatic adenocarcinoma from rectal cancer with massive garland necrosis. Diagnostic physicians should note that rectal cancer can, though extremely rarely, metastasize to the prostate and that the presence of garland necrosis can make image diagnosis difficult.