Iris and Ciliary Body Melanocytomas Are Defined by Solitary GNAQ Mutation Without Additional Oncogenic Alterations

Abstract

To analyze the genetic features of melanocytomas and melanomas of the anterior uvea and assess the value of molecular testing for diagnosis and prognostication. Retrospective case-control study. Patients with melanocytoma (n= 16) and melanoma (n= 19) of the anterior uvea. Targeted next-generation sequencing was performed on formalin-fixed, paraffin-embedded tumor tissue from anterior uveal melanocytic tumors and correlated with clinicopathologic features. Presence or absence of accompanying oncogenic alterations beyond GNAQ/GNA11 and their association with histologic features and local recurrence. Hotspot missense mutations in GNAQ/GNA11 were identified in 91% (32/35) of all cases. None of the melanocytomas with or without atypia demonstrated chromosomal imbalances or additional oncogenic variants beyond GNAQ mutation, and none recurred over a median follow-up of 36 months. Additional alterations identified in a subset of melanomas include mutations in BAP1 (n= 3), EIF1AX (n= 4), SRSF2 (n= 1), PTEN (n=1), and EP300 (n= 1); monosomy 3p (n= 6); trisomy 6p (n= 3); trisomy 8q (n= 2); and an ultraviolet mutational signature (n= 5). Local recurrences were limited to melanomas, all of which demonstrated oncogenic alterations in addition to GNAQ/GNA11 (n= 5). A single melanoma harboring GNAQ and BAP1 mutations and monosomy 3 was the only tumor that metastasized. In this study, anterior segment uveal melanocytomas did not display oncogenic alterations beyond GNAQ/GNA11. Therefore, they are genetically similar to uveal nevi rather than uveal melanoma based on their molecular features known from the literature. Molecular testing can be performed on borderline cases to aidrisk stratification and clinical management decisions.