The T1799A BRAF mutation is present in iris melanoma

PURPOSE: An activating mutation in exon 15 of the BRAF gene has been found in a high proportion of cutaneous pigmented lesions, but only in one case of uveal melanoma. Iris melanoma is the least common uveal melanoma and displays a less aggressive clinical course compared with posterior uveal melanoma. To date, no study has been conducted to investigate the T1799A mutation in iris melanoma. The purpose of this study was to determine whether the T1799A BRAF mutation is present in iris melanoma.

METHODS: DNA was extracted from 19 archival, paraffin-embedded tissue sections of iris melanomas. Nested PCR was used to amplify exon 15 of the BRAF gene, and the product was purified, cloned into a sequencing vector, and sequenced. The sequences obtained were compared with the wild-type sequence of the BRAF gene. The presence or absence of the BRAF mutation was also compared with the clinicopathological features.

RESULTS: The T1799A mutation was identified by sequencing in 9 of 19 iris melanomas. Six of the 9 cases with the BRAF mutation were recurrent tumors. All other tumors were resections for primary tumors. There was a statistically significant association between the BRAF mutation and recurrent tumor (P = 0.003). There was no association between the presence of the BRAF mutation and other clinicopathological characteristics.

CONCLUSIONS: In this small study, the T1799A BRAF mutation was identified in almost half of the iris melanoma tissues samples examined. This finding suggests that there may be genetic as well as clinical differences between iris and posterior uveal melanomas.