title: 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.
abstract: Muir-Torre syndrome (MTS) is a rare autosomal-dominant disorder characterized by the predisposition to both sebaceous skin tumors (or multiple keratoacanthomas) and internal malignancies. A subtype of MTS is allelic to hereditary nonpolyposis colorectal cancer and is caused by germline mutations in the DNA mismatch repair genes MSH2 or MLH1. In these cases both internal and skin tumors show characteristic microsatellite instability (MSI). The aim of the present study was to determine whether immunohistochemical examination of MSH2 or MLH1 protein expression in MTS-associated skin tumors can be used as a diagnostic screening tool to identify patients with germline mutations in MSH2 or MLH1. In the present study 28 skin lesions from 17 patients (20 sebaceous gland tumors, 4 sebaceous hyperplasias, 3 keratoacanthomas, and 1 squamous cell carcinoma) were tested immunohistochemically with antibodies against MSH2 and MLH1. Eighteen of these tumors were from eight patients with known MSH2 germline mutations, two tumors were from a patient with a germline mutation in MLH1, and eight microsatellite stable sporadic skin tumors served as controls. One sample had to be excluded because of a lack of immunoreactivity. All eight microsatellite stable tumors expressed both DNA repair proteins. In 15 of the tumors from MSH2 germline mutation carriers, loss of MSH2 expression was observed, one tumor showed reduced MSH2 expression, and one tumor displayed positive immunoreactivity to MSH2. Both tumors of the MLH1 germline mutation carrier showed loss of the MLH1 protein. In conclusion, our findings demonstrate that immunohistochemical testing of MTS-related skin tumors is a reliable screening method with high predictive value for the diagnosis of the DNA mismatch repair-deficient MTS.
authors.affiliation: Institute of Pathology, University of Bonn, Bonn, Germany. mathiak@ukb.uni-bonn.de
authors.forename: Micaela
authors.initials: M
authors.lastname: Mathiak
authors.forename: Arno
authors.initials: A
authors.lastname: Rütten
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Mangold
authors.forename: Hans-Peter
authors.initials: HP
authors.lastname: Fischer
authors.forename: Thomas
authors.initials: T
authors.lastname: Ruzicka
authors.forename: Waltraut
authors.initials: W
authors.lastname: Friedl
authors.forename: Peter
authors.initials: P
authors.lastname: Propping
authors.forename: Roland
authors.initials: R
authors.lastname: Kruse
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D020137:Base Pair Mismatch; D002352:Carrier Proteins; D003123:Colorectal Neoplasms, Hereditary Nonpolyposis / Q000473:pathology*; D004260:DNA Repair; D004273:DNA, Neoplasm / Q000235:genetics*; D004268:DNA-Binding Proteins; D018095:Germ-Line Mutation; D006801:Humans; D007150:Immunohistochemistry; D018895:Microsatellite Repeats; D000070957:MutL Protein Homolog 1; D051718:MutS Homolog 2 Protein; D009363:Neoplasm Proteins / Q000032:analysis*; D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins / Q000032:analysis* / Q000235:genetics; D012626:Sebaceous Gland Neoplasms / Q000235:genetics* / Q000473:pathology
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D004273:DNA, Neoplasm; D004268:DNA-Binding Proteins; C501486:MLH1 protein, human; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins; C497172:MSH2 protein, human; D000070957:MutL Protein Homolog 1; D051718:MutS Homolog 2 Protein