title: Lymph node metastases of melanoma: challenges for BRAF mutation detection.
abstract: Detection of B-Raf proto-oncogene, serine/threonine kinase (BRAF) mutations is required to predict response to BRAF or mitogen-activated protein kinase kinase 1 and 2 inhibitors in metastatic melanoma. Lymph node (LN) specimens carrying melanoma cells intermingled with abundant lymphocytes often contain low tumor cellularity. This study is aimed to examine challenges in the clinical detection of BRAF mutations in LN specimens with metastatic melanoma and to illustrate characteristic features of p.V600E and non-p.V600E mutations. In this retrospective study for quality assessment of the pyrosequencing assay, we compared characteristics of 53 LN and 135 non-LN formalin-fixed, paraffin-embedded specimens with metastatic melanoma submitted for BRAF mutation detection over a 40-month period. LN specimens showed a significantly higher incidence of p.V600E mutations than non-LN specimens (49% versus 22%, P < .01) but a significantly lower tumor cellularity, particularly in the case of subcapsular or infiltrative metastases. Mutant allele-specific imbalance of the p.V600E mutation was predominantly present in specimens with distant organ metastases (79% versus 27% in LN metastases versus 13% in primary cutaneous tumors or adjacent soft tissue, P < .001). p.V600K was detected in 23% of men older than 60 years old, compared with 6% in women older than 60 years old and 2% in both men and women younger than 60 years old (P < .001). LN specimens with low tumor cellularity due to numerous adjacent lymphocytes may pose a challenge to clinical detection of BRAF mutations of melanoma. The higher incidence of p.V600E mutations in LNs may prompt further studies to elucidate if the p.V600E mutation in primary tumors is associated with a higher risk of LN metastasis.
authors.affiliation: Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, MD, 21287 USA; Department of Pathology, Penn State Hershey Medical Center, Hershey, PA, 17033 USA.
authors.forename: Guoli
authors.initials: G
authors.lastname: Chen
authors.affiliation: Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, MD, 21287 USA; Departments of Pathology, Massachusetts General Hospital, Boston, MA, 02114 USA.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Dudley
authors.affiliation: Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, MD, 21287 USA; Department of Medical Genetics, National Taiwan University Hospital, Taipei, 100, Taiwan.
authors.forename: Li-Hui
authors.initials: LH
authors.lastname: Tseng
authors.affiliation: Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, MD, 21287 USA.
authors.forename: Kirstin
authors.initials: K
authors.lastname: Smith
authors.affiliation: Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, MD, 21287 USA.
authors.forename: Grzegorz T
authors.initials: GT
authors.lastname: Gurda
authors.affiliation: Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, MD, 21287 USA; Department of Oncology, Johns Hopkins University School of Medicine, Baltimore, MD, 21287 USA.
authors.forename: Christopher D
authors.initials: CD
authors.lastname: Gocke
authors.affiliation: Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, MD, 21287 USA; Department of Oncology, Johns Hopkins University School of Medicine, Baltimore, MD, 21287 USA.
authors.forename: James R
authors.initials: JR
authors.lastname: Eshleman
authors.affiliation: Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, MD, 21287 USA. Electronic address: mlin36@jhmi.edu.
authors.forename: Ming-Tseh
authors.initials: MT
authors.lastname: Lin
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D022981:Allelic Imbalance; D001706:Biopsy; D002648:Child; D004252:DNA Mutational Analysis; D005260:Female; D020022:Genetic Predisposition to Disease; D006801:Humans; D008198:Lymph Nodes / Q000201:enzymology / Q000473:pathology*; D008207:Lymphatic Metastasis; D008297:Male; D008545:Melanoma / Q000201:enzymology / Q000235:genetics* / Q000556:secondary*; D008875:Middle Aged; D009154:Mutation; D010641:Phenotype; D011237:Predictive Value of Tests; D011379:Prognosis; D000090063:Proto-Oncogene Mas; D048493:Proto-Oncogene Proteins B-raf / Q000235:genetics*; D012189:Retrospective Studies; D012307:Risk Factors; D012878:Skin Neoplasms / Q000201:enzymology / Q000235:genetics* / Q000473:pathology*; D055815:Young Adult
chemical_list: C000715470:MAS1 protein, human; D000090063:Proto-Oncogene Mas; C482119:BRAF protein, human; D048493:Proto-Oncogene Proteins B-raf
keywords: BRAF; Lymph node; Melanoma; Mutant allele-specific imbalance; Tumor cellularity