Genetic Profiling of Primary Orbital Melanoma: An Analysis of 6 Cases with Clinicopathologic Correlation.

ABSTRACT

PURPOSE: To analyze the genetic profile of 6 cases of primary orbital melanoma with clinicopathologic correlation. DESIGN: Retrospective noninterventional study to analyze the genetic profile of 6 cases of primary orbital melanoma and to correlate the genetic findings with prognosis and clinicopathologic features. Inclusion criteria were patients with primary orbital melanoma with no evidence of primary eyelid skin, conjunctival, uveal, or remote melanoma at extraocular sites. PARTICIPANTS: The study involved 6 primary orbital melanomas from 6 patients. Four patients were exenterated and 2 had incisional biopsies performed. METHODS: Clinical notes and radiologic records were assessed to ascertain clinical tumor behavior. Sections were stained with hematoxylin-eosin and exposed to immunohistochemistry for S100, MelA, HMB45, Sox10, and BAP1. Melanoma DNA was exposed to array comparative genomic hybridization to assess gross chromosomal copy number changes. Point mutation assessment and Sanger sequencing were performed for GNAQ, GNA11, BRAF, NRAS, pTERT, SF3B1, and EIF1AX. MAIN OUTCOME MEASURES: These were the presence of gross chromosomal copy number changes and the presence of mutations in GNAQ, GNA11, BRAF, NRAS, pTERT, SF3B1, and EIF1AX; the presence of metastases and time period between diagnosis and death from melanoma; and correlation between the tumor genetic profile and the clinical behavior of the tumor. RESULTS: One of the 6 cases was clinically associated with oculodermal melanocytosis. Of the 6 patients, 3 died of melanoma metastases and 1 of unrelated causes; 2 remain alive at last review. Three of the 6 cases were histologically associated with a benign precursor lesion. All melanomas expressed S100, MelA, HMB45, and Sox10. One patient showed loss of BAP1 nuclear staining. The most frequent chromosomal gains across the 6 cases, in order of frequency, were 6p, 8q, 17q, 6q, and 20p. The most frequently lost regions were 1p, 9p, 16q, and 17p. One patient showed monsomy 3 and gain of 8q (and showed the BAP1 loss). Mutations were found in GNAQ (1 case), GNA11 (1 case), SF3B1 (2 cases), NRAS (2 cases), and pTERT (2 cases). CONCLUSIONS: The data point to 2 genetic groups for primary orbital conjunctiva melanoma-like and a uveal melanoma-like group. A larger study would help confirm this suggestion.