Oral Presentation ASPCR-ASDR Conference 2013

Immunohistochemical analysis of BRAF V600E staining of primary melanomas arising in association with a naevus. (#43)

Hojabr Kakavand 1 2 , Oana Crainic 3 4 , Trina Lum 3 , John F Thompson 1 2 5 , Georgina V Long 1 2 , Richard A Scolyer 1 2 3
  1. University of Sydney, Camperdown, NSW, Australia
  2. Melanoma Institute Australia, North Sydney, NSW, Australia
  3. Tissue Pathology and Diagnostic Oncology, Royal Prince Alfred Hospital, Camperdown, NSW, Australia
  4. Canterbury Health Laboratories, Canterbury, NSW, Australia
  5. Department of Melanoma and Surgical Oncology, Royal Prince Alfred Hospital, Camperdown, NSW, Australia

BRAF V600E mutations are considered an early event in the development of melanocytic tumours with reported rates of up to 82% in common acquired naevi. 30-50% of melanomas are reported to arise within a pre-existing naevus. The aims of this study were to determine the frequency of BRAF V600E mutations in this group and the concordance between the primary melanoma and the associated naevus.

Formalin-fixed, paraffin-embedded (FFPE) tissue samples from 30 patients containing primary melanomas arising in association with a naevus were identified. Two 4µm sections were cut and a haematoxylin and eosin slide was assessed for the presence of primary melanoma and naevus cells within the same FFPE block. Immunohistochemical staining was carried out with the VE1 antibody (Spring Bioscience) as per the manufacturer’s instructions. The VE1 slides were scored by two pathologists (OC and RS) as either positive or negative for the BRAF V600E mutation.

63% of cases stained positive for BRAF V600E, and all cases were concordant between the primary melanoma and the associated naevus. In the VE1 positive cases the intensity of staining was markedly higher in the melanoma cells compared with the naevus.

This is the first study, as far as we are aware, assessing immunohistochemical staining of BRAF V600E in melanomas arising in association with a naevus. The concordance between the primary and the naevus in mutation status suggests that in these cases the melanoma arose from the naevus and these melanomas have a high frequency of BRAF V600E mutations.