BRAF/KRAS gene sequencing of sebaceous neoplasms after mismatch repair protein analysis.
Sebaceous neoplasms are cutaneous markers for the autosomal-dominant Muir-Torre syndrome (MTS). This phenotypic variant of Lynch syndrome (LS) is caused by germline mutations in DNA mismatch repair (MMR) genes. Microsatellite instability or loss of protein expression suggests a mutation or promoter hypermethylation in 1 of the MMR genes. BRAF gene sequencing may help to distinguish between patients with sporadic and LS-associated colorectal carcinomas with loss of MLH1 expression. LS-associated carcinomas are virtually negative for BRAF mutations, but a subset harbors KRAS mutations. The aim of our study was to test sebaceous neoplasms for V600E BRAF or KRAS mutations to determine if these mutations are associated with somatic or germline MMR defects, analogous to colorectal carcinomas. Over a 4-year period, 32 cases comprising 21 sebaceous adenomas, 3 sebaceomas, and 8 sebaceous carcinomas with sufficient material for testing were collected. MMR immunohistochemistry showed that 7 neoplasms had combined loss of MLH1-PMS2, 16 neoplasms had combined loss of MSH2-MSH6, 2 neoplasms had solitary loss of MSH6, and 7 sebaceous neoplasms had intact protein expression. BRAF/KRAS testing revealed all sebaceous neoplasms contained a wild-type BRAF gene. Two (15%) of 13 patients with MTS were found to harbor a KRAS mutation and loss of MLH1 expression. We conclude that a V600E BRAF mutation may not be helpful in distinguishing sporadic from MTS-associated sebaceous neoplasms. Further studies are needed to determine if KRAS mutations are restricted to patients with MTS or are also present in sporadic sebaceous neoplasms.
Department of Pathology, University of Massachusetts Medical School, UMass Memorial Medical Center, Worcester, MA 01605. Electronic address: kcornejo@partners.org.
Kristine M
KM
Cornejo
Department of Pathology, University of Massachusetts Medical School, UMass Memorial Medical Center, Worcester, MA 01605.
Lloyd
L
Hutchinson
Department of Pathology, University of Massachusetts Medical School, UMass Memorial Medical Center, Worcester, MA 01605.
April
A
Deng
Department of Pathology, University of Massachusetts Medical School, UMass Memorial Medical Center, Worcester, MA 01605.
Keith
K
Tomaszewicz
Department of Pathology, University of Massachusetts Medical School, UMass Memorial Medical Center, Worcester, MA 01605.
Matthew
M
Welch
Department of Pathology, University of Massachusetts Medical School, UMass Memorial Medical Center, Worcester, MA 01605.
Stephen
S
Lyle
Department of Pathology, University of Massachusetts Medical School, UMass Memorial Medical Center, Worcester, MA 01605.
Karen
K
Dresser
Department of Pathology, University of Massachusetts Medical School, UMass Memorial Medical Center, Worcester, MA 01605.
Ediz F
EF
Cosar
D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics*; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D053843:DNA Mismatch Repair; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008875:Middle Aged; D000070957:MutL Protein Homolog 1; D009687:Nuclear Proteins / Q000235:genetics*; D011518:Proto-Oncogene Proteins / Q000235:genetics*; D048493:Proto-Oncogene Proteins B-raf / Q000235:genetics*; D016283:Proto-Oncogene Proteins p21(ras); D060888:Real-Time Polymerase Chain Reaction; D012626:Sebaceous Gland Neoplasms / Q000235:genetics*; D018631:ras Proteins / Q000235:genetics*
D048868:Adaptor Proteins, Signal Transducing; C117307:KRAS protein, human; C501486:MLH1 protein, human; D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins; C482119:BRAF protein, human; D048493:Proto-Oncogene Proteins B-raf; D000070957:MutL Protein Homolog 1; D016283:Proto-Oncogene Proteins p21(ras); D018631:ras Proteins
BRAF; KRAS; Lynch syndrome; Microsatellite instability; Mismatch repair genes; Muir-Torre syndrome; Sebaceous neoplasms