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Review
. 2005 Jun;58(6):640-4.
doi: 10.1136/jcp.2004.022509.

BRAF and NRAS mutations are uncommon in melanomas arising in diverse internal organs

C W Wong  1 , Y S Fan, T L Chan, A S W Chan, L C Ho, T K F Ma, S T Yuen, S Y Leung; Cancer Genome Project
Affiliations
Review

BRAF and NRAS mutations are uncommon in melanomas arising in diverse internal organs

C W Wong et al. J Clin Pathol. 2005 Jun.

Abstract

Background: Malignant melanoma arising from different body compartments may be associated with differing aetiological factors and clinical behaviour, and may manifest diverse molecular genetic profiles. Although many studies have focused on cutaneous melanoma, little is known of mucosal and other types of melanoma. In particular, malignant melanoma of soft parts is different from other melanomas in many respects, yet manifests a common melanocytic differentiation. Mutation of BRAF is now known to be common in cutaneous melanomas, and raises possible new therapeutic options of anti-RAF treatment for these patients. Few data are available for non-cutaneous melanomas.

Aims: To study the incidence of BRAF and NRAS mutations in melanomas arising in diverse internal organs.

Methods: Fifty one melanomas from various internal organs were investigated for BRAF and NRAS mutation by direct DNA sequencing.

Results: BRAF and NRAS mutations were found in two and five mucosal melanomas arising from the aerodigestive and female genital tracts (n = 36). Their occurrence is mutually exclusive, giving a combined mutation incidence rate of 19.4% in mucosal melanomas. Both BRAF and NRAS mutations were absent in malignant melanoma of soft parts (n = 7). BRAF mutation was also absent in uveal melanoma (n = 6), but was seen in two of five cutaneous melanomas. The incidence of BRAF or combined BRAF/NRAS mutations in all non-cutaneous groups was significantly lower than published rates for cutaneous melanomas.

Conclusion: Each melanoma subtype may have a unique oncogenetic pathway of tumour development, and only a small fraction of non-cutaneous melanomas may benefit from anti-RAF treatment.

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Figures

Figure 1
Figure 1
Sequence chromatograms showing (A) wild-type sequence in codon 600 in a malignant melanoma of soft parts; (B) the T1799A (V600E) (arrow) mutation in a malignant melanoma of the nasopharynx; and (C) the A1742T (N581I) (arrow) mutation in a malignant melanoma of the vulva.
See this image and copyright information in PMC

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