Primary orbital melanoma

Contrast computed tomography scan showing acontrast-enhancing tumour behind the right globe displacingthe optic nerve The tumour was a solid, dark brownish multinodular mass covered by fat and skeletal muscle, comprising lobulated sheets of epithelioid and spindly melanocytes with vesicular chromatin, prominent nucleoli, and variable amounts of melanin pigment (Figs 2, 3, and 4). Melanoma cells were positive on SOX10 (redchromogen) immunohistochemical staining ([x]200) Ocular melanoma most frequently involves the uveal tract (choroid, ciliary body, and iris) and the conjunctiva, where melanocytes are normally present. According to The Cancer Genome Atlas uveal melanoma project, mutually exclusive mutations in GNAQ, GNA11, CYSLTR2 and PLCB4are the tumour-initiating mutations whereas BAP1,EIF1AX and SF3B1/SRSF2 mutations are associated with prognosis in uveal melanoma.1 In contrast, conjunctival melanoma typically exhibits BRAF,NRAS and NF1 mutations of the MAPK pathway with UV-induced C→T mutation signature.2Orbital soft tissue melanoma is uncommon with [greater than]90% representing secondary tumours as a result of contiguous spread or metastasis from uveal, conjunctival, cutaneous or sinonasal melanomas.3Primary orbital melanoma is exceedingly rare and has been postulated to arise in embryological remnants of melanocytes arrested in the region since a substantial proportion of cases are associated with blue nevus, orbital melanocytosis or oculodermal melanocytosis (nevus of Ota).