A Case of Prostate Cancer Diagnosed by the Discovery of Pararectal Lymph Node Metastases during Sigmoid Colon Cancer Surgery

Abstract

A 65-year-old man tested positive for fecal occult blood in a routine health checkup. Lower gastrointestinal endoscopy showed a 10-mm Ip polyp in the sigmoid colon and a 12-mm Is polyp in the rectum, and endoscopic mucosal dissection was performed. The histopathological diagnosis was adenocarcinoma, tub1>por2, pT1a, Ly1a, V0 for the sigmoid colon lesion and adenocarcinoma, tub1>por2, pT1b (1,750μm), Ly1a, V1a for the rectal lesion, and laparoscopic low anterior resection was performed as an additional procedure. Although there had been no sign of obvious lymph node enlargement on preoperative and intraoperative findings, 4 of the 12 pararectal lymph nodes in the resected specimen showed metastases of poorly differentiated adenocarcinoma. Immunohistostaining results were negative for CK7, CK20, and CDX2, but positive for prostate-specific antigen (PSA), and lymph node metastases of prostate cancer were therefore suspected. Additional tests showed an elevated serum PSA level, and a hypointense mass in both lobes of the prostate was seen on T2-weighted imaging of magnetic resonance imaging. Biopsy confirmed the presence of adenocarcinoma, and prostate cancer was therefore diagnosed. There have been few reports of pararectal lymph node metastases of prostate cancer, and this case in which prostate cancer was diagnosed by the identification of pararectal lymph node metastases in a patient being treated for colorectal cancer is reported, along with a short discussion of the literature.