Uveal Melanoma in a Non-Human Primate

Abstract

Purpose: : This report describes a case of spontaneous uveal melanoma identified in a cynomolgus monkey, with clinical and pathological characteristics in common with those found in humans. Uveal melanoma is the most common primary intraocular malignant tumor of humans however, this tumor has been rarely reported for other species. Because of differences in topographical, histological and behavioral characteristics of spontaneous tumors in other species, uveal melanoma models have been limited to experimental animal models implanted with human uveal melanoma cell lines and transgenic mouse models. A nonhuman primate (NHP) model would be a better anatomical and biologically appropriate alternative to current models. To our knowledge, primary uveal melanoma has not previously been reported in a NHP. This case portends to the possibility of a NHP model of uveal melanoma.

Methods: : An ocular mass was followed over the course of two years by fundus photography, fluorescein angiography, 3 dimensional OCT, and A and B scan ultrasonography. The eye was enucleated and processed using standard methods following euthanasia. EM was done on paraffin processed sections previously mounted on glass slides.

Results: : A slow growing, choroidal mass (3.2 mm x 1.5 mm) with internal circulation and expansion into the macula was identified using standard ophthalmological imaging techniques. Epithelioid and spindle A cells characteristic of mixed pattern human melanoma was observed on histology. Sheets of epitheloid cells containing melanosomes were found on EM. No evidence of systemic disease was identified on clinical pathology or post-mortem examination.

Conclusions: : The mass was diagnosed as a primary uveal melanoma. Communication and vigilance within the broader scientific community could lead to the identification of additional cases, potentially to the establishment of a NHP model.

Keywords: melanoma • comparative anatomy • pathology techniques