A Case of Prostate Cancer Metastasis to the Rectum through Lymphatic Chaneels

Abstract

A 53-year-old man presented with constipation and low back pain. A colonoscopy disclosed a rectal lesion completely encircling the lower rectum. A biopsy of the tissue collected from the same site confirmed poorly differentiated adenocarcinoma. In addition, the serum PSA value was high so that a biopsy of the prostate was carried out. It resulted in Gleason score 9, and we made the diagnosis of prostate cancer. CT and PET-CT scans revealed findings of sclerotic metastatic bone tumor, but the boundary between the prostate and the rectum was relatively clear. We diagnosed the case as bone metastasis of prostate cancer associated with primary rectal cancer. As to the primary rectal cancer, we performed laparoscopic Hartmann's operation. On histopathological studies, epithelial atypia was poor, invasive proliferation of poorly differentiated adenocarcinoma was seen mainly from the submucosa to the serosal side, and the lymph vessels were also filled with tumor cells. The tumor cells were positive in PSA and NKX3.1 staining. From these findings, the final diagnosis of prostate cancer metastasis to the rectum through lymphatic channels was made.