title: Variations of BRAF mutant allele percentage in melanomas.
abstract: BACKGROUND
  BRAF mutations are present in 40% of human skin melanomas. Mutated tumors with an increased percentage of BRAF mutant alleles (BRAF-M%) may have a better response to RAF/MEK inhibitors. We evaluated the BRAF-M% in melanomas, and the genetic causes of its variation.
  
  
  METHODS
  BRAF-M% was quantified by pyrosequencing, real-time PCR (rtPCR) and/or picoliter-droplet PCR (dPCR). BRAF mutant expression was detected by immunohistochemistry. Chromosomal alterations were analyzed with fluorescence in situ hybridization (FISH), and single nucleotide polymorphism (SNP) arrays.
  
  
  RESULTS
  BRAF-M% quantification obtained with pyrosequencing was highly correlated (R = 0.94) with rtPCR, and with dPCR. BRAF-M% quantified from DNA and RNA were also highly correlated (R = 0.98). Among 368 samples with >80% tumor cells, 38.6% had a BRAF (V600E) mutation. Only 66.2% cases were heterozygous (BRAF-M% 30 to 60%). Increased BRAF-M% (>60%) was observed in 19% of cases. FISH showed a polysomy of chromosome 7 in 13.6%, 35.3% and 54.5% of BRAF wild-type, heterozygous and non-heterozygous BRAF-mutated samples, respectively (P < 0.005). Amplification (5.6%) and loss (3.2%) of BRAF locus were rare. By contrast, chromosome 7 was disomic in 27/27 BRAF-mutated nevi.
  
  
  CONCLUSIONS
  BRAF-M% is heterogeneous and frequently increased in BRAF-mutant melanomas. Aneuploidy of chromosome 7 is more frequent in BRAF mutant melanomas, specifically in those with high BRAF-M%.
authors.affiliation: EA4340, Versailles University, Boulogne-Billancourt, France. zofia.helias@aphp.fr.|Department of Pathology, Ambroise Paré Hospital, APHP, Boulogne-Billancourt, France. zofia.helias@aphp.fr.
authors.forename: Zofia
authors.initials: Z
authors.lastname: Hélias-Rodzewicz
authors.affiliation: EA4340, Versailles University, Boulogne-Billancourt, France. elisa.funck-brentano@aphp.fr.|Department of Dermatology, Ambroise Paré Hospital, APHP, Boulogne-Billancourt, France. elisa.funck-brentano@aphp.fr.
authors.forename: Elisa
authors.initials: E
authors.lastname: Funck-Brentano
authors.affiliation: EA4340, Versailles University, Boulogne-Billancourt, France. laure.baudoux@yahoo.fr.
authors.forename: Laure
authors.initials: L
authors.lastname: Baudoux
authors.affiliation: Department of Hospital Pathology, College of Medicine, The Catholic University of Korea, Seoul, Korea. ckjung@catholic.ac.kr.
authors.forename: Chan Kwon
authors.initials: CK
authors.lastname: Jung
authors.affiliation: EA4340, Versailles University, Boulogne-Billancourt, France. us.zimmermann@gmail.fr.|Department of Pathology, Ambroise Paré Hospital, APHP, Boulogne-Billancourt, France. us.zimmermann@gmail.fr.
authors.forename: Ute
authors.initials: U
authors.lastname: Zimmermann
authors.affiliation: EA4340, Versailles University, Boulogne-Billancourt, France. cristi.marin@aphp.fr.|Department of Pathology, Ambroise Paré Hospital, APHP, Boulogne-Billancourt, France. cristi.marin@aphp.fr.
authors.forename: Cristi
authors.initials: C
authors.lastname: Marin
authors.affiliation: EA4340, Versailles University, Boulogne-Billancourt, France. thierryclerici@noos.fr.|Department of Pathology, Ambroise Paré Hospital, APHP, Boulogne-Billancourt, France. thierryclerici@noos.fr.
authors.forename: Thierry
authors.initials: T
authors.lastname: Clerici
authors.affiliation: EA4340, Versailles University, Boulogne-Billancourt, France. legall.catherine@voila.fr.|Department of Pathology, Ambroise Paré Hospital, APHP, Boulogne-Billancourt, France. legall.catherine@voila.fr.
authors.forename: Catherine
authors.initials: C
authors.lastname: Le Gall
authors.affiliation: EA4340, Versailles University, Boulogne-Billancourt, France. frederique.peschaud@aphp.fr.|Department of Surgery, Ambroise Paré Hospital, APHP, Boulogne-Billancourt, France. frederique.peschaud@aphp.fr.
authors.forename: Frédérique
authors.initials: F
authors.lastname: Peschaud
authors.affiliation: INSERM UMR-S1147, University Paris Sorbonne Cite, Paris, France. valerie.taly@parisdescartes.fr.
authors.forename: Valérie
authors.initials: V
authors.lastname: Taly
authors.affiliation: EA4340, Versailles University, Boulogne-Billancourt, France. philippe.saiag@uvsq.fr.|Department of Dermatology, Ambroise Paré Hospital, APHP, Boulogne-Billancourt, France. philippe.saiag@uvsq.fr.
authors.forename: Philippe
authors.initials: P
authors.lastname: Saiag
authors.affiliation: EA4340, Versailles University, Boulogne-Billancourt, France. jean-francois.emile@uvsq.fr.|Department of Pathology, Ambroise Paré Hospital, APHP, Boulogne-Billancourt, France. jean-francois.emile@uvsq.fr.
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Emile
mesh_terms: D000782:Aneuploidy; D002897:Chromosomes, Human, Pair 7 / Q000235:genetics; D006579:Heterozygote; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D008545:Melanoma / Q000453:epidemiology / Q000235:genetics*; D020641:Polymorphism, Single Nucleotide / Q000235:genetics; D048493:Proto-Oncogene Proteins B-raf / Q000235:genetics*; D060888:Real-Time Polymerase Chain Reaction
chemical_list: C482119:BRAF protein, human; D048493:Proto-Oncogene Proteins B-raf