Concordant BRAFV600E mutation status in primary melanomas and associated naevi

implications for mutation testing of primary melanomas

Hojabr Kakavand*, Oana Crainic, Trina Lum, Sandra A. O'Toole, Richard F. Kefford, John F. Thompson, James S. Wilmott, Georgina V. Long, Richard A. Scolyer

*Corresponding author for this work

Research output: Contribution to journalArticle

15 Citations (Scopus)

Abstract

There is concern that BRAF mutant naevus cells admixed with melanoma cells could cause false positive mutation tests in BRAF wild-type melanomas. We sought to assess the frequency of BRAFV600E mutations in primary melanomas arising with/without associated naevi and determine BRAFV600E concordance between melanomas and associated naevi. Formalin fixed, paraffin embedded (FFPE) tissue from 57 patients with primary melanomas with/without associated naevi was immunohistochemically stained to detect BRAF V600E mutation. In a subset of patients (n=29), molecular mutation testing was also carried out using a panel of 238 known genetic variants. Of the primary melanomas with an associated naevus (n=29), 55% were BRAF V600E mutant with 100% concordance between the melanoma and associated naevus. In contrast, only 21% of the primary melanomas unassociated with naevi were BRAFV600E mutant (p=0.009). Our results suggest that melanomas with associated naevi have a higher frequency of BRAFV600E mutations than melanomas unassociated with naevi. Furthermore, melanomas and their associated naevi were concordant in BRAFV600E status, which suggests that false positive mutation tests occurring as a consequence of admixed BRAF mutant naevus cells in BRAF wild-type primary melanomas are unlikely to be a problem in clinical practice. The findings have important implications for adjuvant clinical trials of targeted therapies.

Original languageEnglish
Pages (from-to)193-198
Number of pages6
JournalPathology
Volume46
Issue number3
DOIs
Publication statusPublished - Apr 2014
Externally publishedYes

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