What types of melanomas can present on the eye?

Types of Melanomas Presenting on the Eye

Melanomas can present on the eye in three distinct anatomical locations: uveal melanoma (affecting the iris, ciliary body, or choroid), conjunctival melanoma (on the conjunctival surface), and rarely as metastatic disease from cutaneous melanoma. 1

Uveal Melanoma (Intraocular)

Uveal melanoma is the most common primary intraocular malignancy in adults, with specific anatomical distributions: 2, 3

• Choroidal melanoma (90% of uveal melanomas) - arises from melanocytes in the choroid, typically presenting as a dome-shaped pigmented mass 1, 4
• Ciliary body melanoma (6% of uveal melanomas) - can involve ciliary body alone or extend to adjacent structures 1, 2
• Iris melanoma (4% of uveal melanomas) - the least common uveal location 2, 4

Key Clinical Features

Uveal melanomas are genetically distinct from cutaneous melanomas, predominantly harboring GNAQ or GNA11 mutations rather than BRAF mutations, which fundamentally affects treatment approaches. 1, 3, 5

The pathology report should document: 1

• Specific tissue involvement (choroid only, choroid and ciliary body, ciliary body only, iris and ciliary body, or iris only)
• Tumor dimensions and location by clock hour
• Color characteristics (melanotic, amelanotic, or variegated)
• Presence of extraocular extension or involvement of intrascleral emissary channels

Conjunctival Melanoma

Conjunctival melanoma presents as a painless, flat or nodular brown or fleshy-pink lesion on the bulbar or palpebral conjunctiva or caruncle. 1, 6

Warning Signs Requiring Urgent Evaluation

• Enlargement of the lesion 6, 7
• Development of blood vessels or thickening 6, 7
• Recurrence in the same location 6

Risk Factors

• Significant UV exposure 1, 7
• Previous history of melanoma 1, 7
• Previous primary acquired melanosis or Nevus of Ota 1, 7

Pathologic Assessment Requirements

The pathology report must include: 1

• Presence or absence of invasion into underlying tissues (episclera, corneal stroma)
• Tumor status at all resection margins (deep and lateral)
• Tumor thickness in millimeters (measured by Jakobiec method)

Critical Distinctions from Cutaneous Melanoma

Mucosal and uveal melanomas differ significantly from cutaneous melanoma in presentation, genetic profile, staging, response to treatment, and patterns of progression. 1

Genetic Profiles by Subtype

• Non-chronic sun damage cutaneous melanoma: 56% BRAF mutations 1
• Uveal melanoma: Predominantly GNAQ/GNA11 mutations, 0% BRAF mutations 1, 3, 5
• Mucosal melanoma: 3% BRAF mutations, 39% KIT aberrations 1

Metastatic Potential

• Conjunctival melanoma tends to spread to other adnexal structures and has metastatic potential to regional lymph nodes 7
• Uveal melanoma has approximately 50% risk of developing metastatic disease, usually involving the liver, which is typically fatal within 1 year 3, 5

Common Pitfalls to Avoid

• Do not assume all ocular melanomas respond to cutaneous melanoma treatments - immune checkpoint inhibitors effective in cutaneous melanoma show limited effects in uveal melanoma due to distinct genetics 5, 8
• Do not miss conjunctival melanoma masquerading as benign lesions - any yellowish or brownish conjunctival spot in elderly patients requires slit-lamp biomicroscopy and consideration of biopsy for atypical features 6
• Do not delay evaluation of changing pigmented lesions - documentation of growth, thickness >2mm, presence of subretinal fluid, or orange pigment are risk factors requiring immediate intervention 4