What happened, in summary

A woman with a history of recurrent sebaceous tumors and a strong family history of colorectal cancer underwent colonoscopy after clinicians suspected Muir-Torre syndrome. Although she had no gastrointestinal symptoms, a lesion was found in the cecum. She underwent right hemicolectomy followed by adjuvant chemotherapy. Pathology showed a well-differentiated adenocarcinoma with small mucinous areas and no lymph-node involvement. Molecular testing of the colon tumor showed high microsatellite instability and loss of MSH2 protein expression. Sequencing identified a truncating MSH2 mutation, supporting an inherited mismatch-repair syndrome. Her history also included endometrial cancer with ovarian metastases and multiple sebaceous neoplasms, fitting the broader Muir-Torre pattern. The colorectal diagnosis became an important part of recognizing the hereditary syndrome and the need for lifelong cancer surveillance and genetic counseling for the patient and family.