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Ough pathways mediated by IGFBP7 [24?6]. Most nevi, including so called "dysplastic nevi", cease proliferation and remain static for decades. If nevi are indeed precursor lesions of melanoma they must acquire genetic alterations to free themselves of growth restraints and becomeNRAS and BRAF in Melanoma-Associated [https://www.medchemexpress.com/Arg-Gly-Asp-Ser.html Arg-Gly-Asp-Ser web] Nevimalignant. The fact that oncogenic BRAF mutations are frequent in "dysplastic nevi", congenital nevi, common nevi and especially in growing nevi [20,27,28] has challenged the role of BRAF mutations for the development of melanoma [16] in particular and the model of stepwise tumor progression in general. According to this model the "dysplastic" or "atypical nevus" is the "missing link" between a benign and a malignant melanocytic lesion [4] and should be typified by genetic alterations that differ from "common nevi" and from melanoma. The major inherent problem is the lack of interobserver agreement for the morphology-based diagnosis of "dysplastic nevi" including clinical, dermatoscopic and histopathologic diagnosis [29]. Until now, BRAF or NRAS mutations have been investigated systematically only in nevi that were not associated with melanomas [7,10,20,22,30,31]. Therefore it is unknown if BRAF or NRAS mutations play any role in the progression of a nevus into a melanoma. For a better understanding it is mandatory to study a subset of melanomas that arose in association with a preexisting nevus [32,33]. To gain a more profound understanding in the [http://www.ncbi.nlm.nih.gov/pubmed/18204824 18204824] role of BRAF or NRAS mutations in the development of melanoma from nevi we compared the genotype and BRAFV600E protein [http://www.ncbi.nlm.nih.gov/pubmed/ 23148522  23148522] expression of melanomas and their associated nevi with control nevi of the same patient.Table 1. Mutations detected in samples.Matched BRAFV600 (Sanger) V600E V600K Wildtype BRAFV600EMelanoma (n=45) 51.1  (n=23) 0 48.9  (n=22) Melanoma (n=46) 63.0  (n=29) 37.0  (n=17) Melanoma (n=42) 2.4  (n=1; A66A) 4.8  (n=2) 2.4  (n=1) 2.4  (n=1) 88.1  (n=37)Associated nevus (n=46) 63.0  (n=29) 0 37.0  (n=17) Associated nevus (n=46) 65.2  (n=30) 34.8  (n=16) Associated nevus (n=44) 2.3  (n=1; L52L) 4.5  (n=2) 2.3  (n=1) 9.1  (n=4) 81.8  (n=36)Control 52.0  (n=13) 4.0  (n=1) 44.0  (n=11) Control nevus (n=25) 54.2  (n=13) 48.0  (n=12) Control nevus (n=21)melanomanevus (n=25) (n=28) 39.3  (n=11) 0 60.7  (n=17) Matched melanoma (n=29) 41.4  (n=12) 58.6  (n=17) Matched melanoma (n=26)(Sanger + VE1 IHC) V600E Wildtype NRAS Exon 2 (Sanger) Silent mutations Q61K Q61L Q61R Wildtype14.3  (n=3) 0 0 0 85.7  (n=18) 0 7.7  (n=2) 92.3  (n=24)ResultsPatient characteristicsWe included 46 melanomas (from 45 patients) that developed in association with a preexisting nevus. Mean age of the patients at diagnosis was 51.4 years (SD ?5.5), 34.8  were female. In 25 patients a suitable control-nevus of the same patient was also available for genetic analysis. The majority of melanomas (74.2 ) had a Breslow thickness