We performed an immunohistochemical study with antibodies against MSH6, MSH2, MLH1, and PMS2, which demonstrated preserved nuclear expression of the mismatch repair proteins, therefore ruling out Muir-Torre syndrome.
Mutations reported to cause Muir-Torre syndrome (MTS) have previously been reported in the mismatch repair genes MLH1 and MSH2 and more recently, in MYH [1].
Evidence indicating microsatellite stability in three of 17 patients with a clinical history indicative of Muir-Torre syndrome and a mutation in only MSH-6 suggests that the phenotype of a germline MSH-6 mutation differs from that of MLH-1 and MSH-2 mutations and further supports the use of immunohistochemistry as a screening tool in patients with Muir-Torre syndrome with an extended panel that includes MSH-6.
All 10 sporadic periocular sebaceous carcinomas maintained strong staining of the 4 mismatch repair genes, while tumor from the patient with Muir-Torre syndrome showed loss of staining for the mismatch repair genes MSH2 and MSH6.
In this study, we report a 74-year-old man with known Muir-Torre syndrome with confirmed MSH2 germline mutation, diagnosed with pleomorphic liposarcoma of the right buttock in a previous radiation field.
Loss of DNA mismatch repair proteins in skin tumors from patients with Muir-Torre syndrome and MSH2 or MLH1 germline mutations: establishment of immunohistochemical analysis as a screening test.
Haplotype analysis showed that the kindreds C and V+Va (both from northeastern Italy, both displaying clinical features of the Muir-Torre syndrome) shared a seven-locus haplotype, indicating that the MSH2 1-6 deletion is probably a founder mutation.
Having a high probability for MSI, she was found to be heterozygous for a germline point mutation in MSH2 gene, where a pathologic variant, c.1165C > T (p.Arg389*), determined by sequencing confirmed Muir-Torre syndrome (MTS).
Mutations reported to cause Muir-Torre syndrome (MTS) have previously been reported in the mismatch repair genes MLH1 and MSH2 and more recently, in MYH [1].
Most examples of hereditary non-polyposis cancer syndrome (Lynch syndrome), including the Muir-Torre syndrome, are associated with microsatellite instability (MSI) and germline mutations in mismatch repair genes-most commonly MLH1 or MSH2.
We report a case of Muir-Torre syndrome associated with intrahepatic cholangiocarcinoma, a location not previously described, and associated with a novel missense mutation of the MSH2 gene (c.2026T > C), predicted to disrupt the function of the gene.