Colonic ganglioneuromatous polyposis and metastatic adenocarcinoma in the setting of Cowden syndrome: a case report and literature review.

Cowden syndrome is a rare, autosomal-dominant, multisystem disorder characterized by hamartomatous tissue overgrowth and an increased risk of breast, thyroid, and endometrial cancers. Most of the cases arise from germline mutations of the phosphatase and tensin homologue tumor suppressor gene. An association with colon cancer remains unproven but has been suggested in previous reports. We present the case of a 42-year-old man with colonic ganglioneuromatous polyps and an adjacent colonic adenoma giving rise to a signet-ring adenocarcinoma with lymph node metastases in the setting of Cowden syndrome. Although gastrointestinal polyps are a common feature of Cowden syndrome, reports of ganglioneuromatous polyps and malignant degeneration are rare. Cutaneous features of Cowden syndrome in our patient include "cobblestone" lesions of the tongue and oral mucosa, facial trichilemmomas, multiple acral keratoses, and a storiform collagenoma.