Journal
PATHOLOGY
Volume 46, Issue 3, Pages 193-198Publisher
ELSEVIER SCIENCE BV
DOI: 10.1097/PAT.0000000000000077
Keywords
BRAF; diagnosis; immunohistochemistry; melanoma; mutation testing; naevus; pathology; targeted therapy; treatment
Categories
Funding
- University of Sydney
- Melanoma Institute Australia
- Cancer Institute NSW
- NHMRC
- Cancer Institute NSW Fellowship program
- Cancer Institute NSW Clinical Research Fellowship
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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 BRAF(V600E) mutations in primary melanomas arising with/without associated naevi and determine BRAF(V600E) 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 BRAF(V600E) mutant (p=0.009).Our results suggest that melanomas with associated naevi have a higher frequency of BRAF(V600E) mutations than melanomas unassociated with naevi. Furthermore, melanomas and their associated naevi were concordant in BRAF(V600E) 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.
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