Muir-Torre Syndrome: A Case Report in a Woman Without Personal Cancer History

Area of Science:

• Oncology
• Genetics
• Dermatology

Background:

• Muir-Torre syndrome (MTS) is a rare autosomal dominant disorder characterized by sebaceous neoplasms and a predisposition to various cancers, particularly colorectal cancer.
• Sebaceous neoplasms, including adenomas and sebaceomas, can be indicative of underlying genetic syndromes like MTS.
• Microsatellite instability (MSI) is a molecular hallmark of DNA mismatch repair deficiency, often associated with Lynch syndrome and MTS.

Observation:

• A 68-year-old woman presented with multiple sebaceous neoplasms (adenoma to sebaceoma).
• Immunohistochemistry for microsatellite instability (MSI) on sebaceous adenomas showed absent MSH2 and MSH6 expression but retained MLH1 and PMS2.
• Germline sequencing identified a pathogenic MSH2 gene mutation (c.1165C > T, p.Arg389*).

Findings:

• The patient was diagnosed with Muir-Torre syndrome (MTS) based on clinical presentation and genetic findings.
• MSI testing by immunohistochemistry (IHC) effectively identified potential Lynch syndrome-associated mutations.
• The patient's son was diagnosed with colon cancer, also linked to his MTS.

Implications:

• This case underscores the utility of MSI testing (IHC and sequencing) in diagnosing suspected MTS.
• Identifying MTS has significant implications for cascade genetic testing and cancer risk management in affected families.
• Early detection through comprehensive genetic evaluation can improve patient outcomes and inform family members about their cancer risks.