Metastatic colon cancer derived from a diverticulum incidentally found at herniorrhaphy: a case report

BACKGROUND: There are few reports of metastases from colon cancer to an inguinal hernia sac, and few reports of colon cancer originating in diverticula. We report a patient with carcinoma of the sigmoid colon arising in two diverticula, who presented with peritoneal seeding to an inguinal hernia sac, and a review of the literature. CASE PRESENTATION: A 55-year-old male underwent open herniorrhaphy for a left inguinal hernia. At operation, a nodule in the inguinal hernia sac was resected and histologic examination revealed adenocarcinoma, which was suspected to be a metastasis from a distant primary lesion. Postoperative evaluation included colonoscopy and positron emission tomography which showed two suspected lesions in sigmoid diverticula. Laparoscopic subtotal colectomy was performed, and pathology revealed adenocarcinoma in two sigmoid diverticula. CONCLUSIONS: If a nodule is found in an inguinal hernia sac, especially in older patients, peritoneal metastases should be considered. Resection of the nodule with histopathologic evaluation is essential. Colon cancer arising in a diverticulum should be considered as a possible site of the primary lesion.