BRAF mutation status in primary and metastatic melanomas in two regions with differing potential ultraviolet radiation exposure.

BACKGROUND: Melanoma is seen as a heterogeneous molecular entity, with solar ultraviolet radiation (UVR) and BRAF mutation status being important determinants. AIM: To study primary and metastatic melanomas from two UVR-distinct regions to elucidate correlations between prognostic predictors, UVR and BRAF mutation status. METHODS: Extended BRAF testing for 9 mutations was obtained for 95 primary melanomas [Lebanon (LB) n = 55, Pakistan (PK) n = 40)] and 65 metastatic melanomas (LB n = 36, PK n = 29). Collected data included patient age and sex, melanoma size and anatomical location, prognostic parameters and solar elastosis grade for primary melanomas. For metastatic melanomas, site of metastasis, magnitude of necrosis and degree of pigmentation were assessed. Cumulative 21-year averages of potential UVR exposure for Lebanon (110 kJ/m(2) /year) and Pakistan (128 kJ/m(2) /year) were derived from the National Center for Atmospheric Research databases. RESULTS: BRAF mutation status was obtained for 146/160 cases (91.3%). Overall mutation rate was 24/88 (27.3%) in primary and 25/58 (43.1%) in metastatic melanoma. V600E was the predominant mutation in 21/24 (87.5%) of primary and 23/25 (92%) of metastatic melanomas. A 60% discordant mutation rate was identified; of three patients, two lost the mutation in the metastasis and one gained it. The relative incidence of BRAF mutation with potential UVR exposure showed a similar trend in primary (low vs. high UVR: 32.1% vs. 20.0%) and metastatic (57.1% vs. 21.7%) melanomas (P < 0.05). Predictors of BRAF mutations were trunk location and epithelioid and mixed cytology for primary and subcutaneous metastasis, low UVR exposure and absence of pigmentation for metastatic melanomas (P < 0.05). BRAF-positive status in primary melanomas was predicted by multivariate binary logistic regression with reasonable accuracy (C-statistic = 0.67, 95% CI 0.530-0.81 with one independent predictor, namely, epithelioid cytology (OR = 5.11, 95% CI 1.38-8.88, P = 0.01). In metastatic melanomas, high UVR (OR = 0.21, 95% CI 0.06-0.07; P < 0.01) was an independent negative predictor of BRAF mutation. CONCLUSIONS: We have documented the rate of different BRAF mutation types in a Lebanese and Pakistani cohort, and assessed correlations with prognostic markers and potential UVR exposure.

BRAF mutational epidemiology in dysplastic nevi: does different solar UV radiation exposure matter?

BACKGROUND: Proto-oncogene B-Raf (BRAF) mutation rates have been reported in nevi and melanomas of homogeneous Caucasian cohorts. OBJECTIVE: To study the demographics of BRAF mutations in dysplastic nevi of populations with differing potential solar UV radiation exposure. METHODS: Extended BRAF testing for 9 mutations in 125 dysplastic nevi from 101 patients, derived from populations with differing potential UV radiation exposure rates (Lebanon and Saudi Arabia), was performed. Clinical and microscopic parameters were recorded. RESULTS: BRAF mutation status was carried out for 101/125 (80.8%) cases with an overall mutation rate of 62.4% (63/101). V600E (c.1799T > A) was the predominant mutation, found in 61/63 (96.8%) cases. BRAF mutation rate differed significantly by potential UV radiation exposure (Lebanon: 53.4%, Saudi Arabia: 74.4%, P < 0.05). A 43.8% discordant mutation rate (7/16 patients) was found in patients with multiple nevi, including 2 patients with different BRAF mutations. Microscopic examination subdivided the dysplasia into mild (n = 24), moderate (n = 60) and severe (n = 41) with trunk predominance (72.8%). Higher rates of pigment in the stratum corneum were identified in Saudi Arabia (P < 0.05). No statistical significant increase in BRAF mutation rate was noted with advanced architectural and cytological atypia. Parameters associated with a negative BRAF mutation status included upper extremity location, regression, cohesiveness and presence of suprabasal melanocytes (P < 0.05). Positive BRAF mutation status was reasonably predicted by multivariate binary logistic regression by 2 independent predictors: Geographic location and compound nevus type. CONCLUSIONS: In our Near Eastern cohort, the BRAF mutation rate varied significantly by geographic location. In patients with multiple dysplastic nevi examined, discordant BRAF mutation status potentially negates an underlying constitutional predilection.