In this case report of Muir-Torre syndrome (MTS), we describe a 47-year-old man with a personal and family history of colon cancer and a personal history of keratoacanthoma who presented with a sebaceous carcinoma and, subsequently, had a cystic sebaceous tumor. Immunohistochemical examination of the patient's colonic tumor, located proximal to the splenic flexure, revealed absence of MutL homolog (MLH)-1 protein. MTS is a rare genodermatosis defined clinically by the occurrence of a sebaceous neoplasm and an internal malignancy in the absence of other predisposing factors. Most patients present with sebaceous adenomas, but cystic sebaceous neoplasms have been reported as specific markers of MTS. Gastrointestinal and genitourinary cancers are the most common internal malignancies, with colorectal cancers often occurring at or proximal to the splenic flexure, contrary to most sporadic colorectal cancers. MTS is most frequently found as a variant of the autosomal dominant disorder hereditary non-polyposis colorectal cancer (HNPCC), with tumors demonstrating microsatellite instability and germline mutations in the DNA mismatch repair genes MutS homolog (MSH)-2 and MLH1. However, the distribution of gene mutations of patients with MTS is slightly different from that seen in all HNPCC families, and some cases of MTS arise spontaneously. Physicians should consider MTS in patients presenting with a sebaceous neoplasm, and immunohistochemical examination of tumors for MSH2 and MLH1 protein can be used as a screening test to identify patients with MTS. While the sebaceous and internal neoplasms of MTS are thought to follow a more indolent course than sporadic malignancies, patients with this disorder should be treated with standard therapies and carefully followed. Evidence indicates that for individuals with or at risk of MTS or HNPCC, colonoscopy every 1-2 years beginning at age 20-25 or 10 years younger than the youngest age at diagnosis in the family can be strongly recommended. Additionally, most experts believe that an annual history and physical examination, including a complete skin examination and urinalysis, as well as periodic endometrial sampling and/or transvaginal ultrasound for women, are worthwhile screening tests for these high-risk patients.