title: An illustrative case of Muir-Torre syndrome: contribution of immunohistochemical analysis in identifying indicator sebaceous lesions.
abstract: BACKGROUND
  Muir-Torre syndrome (MTS) is an autosomal dominant genodermatosis characterized by the association of at least 1 cutaneous sebaceous tumor and 1 internal malignancy, often arising in the gastrointestinal tract. It is secondary to germline mutations in DNA mismatch repair genes, mainly MLH-1 and MSH-2.
  
  
  METHODS
  We report the case of a 54-year-old man with a 2-year history of skin-colored papules clinically reminiscent of large sebaceous hyperplasias on the nose and back, but histologically diagnosed as sebaceous adenomas and epitheliomas. His family history was positive for colon cancer in the mother and 2 brothers. A colonoscopy done during the hospitalization revealed 2 sessile polyps in the left colon, both showing a low-grade dysplasia on the biopsy specimen. Immunohistochemical staining performed on the cutaneous and colic biopsy specimens revealed a lack of expression of MSH-2 and MSH-6. Genetic testing revealed microsatellite instability in the colon and cutaneous tumors.
  
  
  CONCLUSIONS
  The immunohistochemical testing for MSH-2, MSH-6, and MLH-1 is useful for rapid identification of an underlying mismatch repair defect and early diagnosis of MTS.
authors.affiliation: Department of Dermatology, Geneva University Hospital, 24 Rue Micheli-du-Crest, CH-1211 Geneva 14, Switzerland. gionata.marazza@hcuge.ch
authors.forename: Gionata
authors.initials: G
authors.lastname: Marazza
authors.forename: Isabelle
authors.initials: I
authors.lastname: Masouyé
authors.forename: Sophia
authors.initials: S
authors.lastname: Taylor
authors.forename: Christa
authors.initials: C
authors.lastname: Prins
authors.forename: Thomas
authors.initials: T
authors.lastname: Gaudin
authors.forename: Jean-Hilaire
authors.initials: JH
authors.lastname: Saurat
authors.forename: Lars E
authors.initials: LE
authors.lastname: French
mesh_terms: D018266:Adenocarcinoma, Sebaceous / Q000175:diagnosis* / Q000378:metabolism / Q000473:pathology; D001415:Back / Q000473:pathology; D003123:Colorectal Neoplasms, Hereditary Nonpolyposis; D003937:Diagnosis, Differential; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008875:Middle Aged; D051718:MutS Homolog 2 Protein / Q000378:metabolism; D009666:Nose / Q000473:pathology; D012626:Sebaceous Gland Neoplasms / Q000175:diagnosis* / Q000378:metabolism / Q000473:pathology
chemical_list: C497172:MSH2 protein, human; D051718:MutS Homolog 2 Protein