Excerpt from Melanoma, Conjunctival

Synonyms, Key Words, and Related Terms: conjunctival melanoma, malignant melanoma of the conjunctiva, malignancy, tumor, exenteration, cryotherapy

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Background: Malignant melanoma of the conjunctiva presents as a raised, pigmented or nonpigmented lesion that appears in adult life. This lesion is uncommon but potentially lethal. It can arise in previously unblemished and unpigmented regions (approximately 10% of cases), from a preexisting nevus (approximately 20% of cases), or from the flat spreading pigmentation of primary acquired melanosis with atypia (60-70% of cases).

Pathophysiology: Primary site: Together with mucus-secreting goblet cells within the stratified epithelium, melanocytic cells exist in the basal layer of the conjunctiva. These melanocytic cells are of neuroectodermal origin, and melanocytic tumors may arise from these cells.

Melanomas may arise from junctional and compound nevi. Some uncertainty exists regarding the role of nevi in the histogenesis of malignant melanoma. Previously, compressed cells at the melanoma base have been considered to be nevi, but recent reports suggest that these flattened cells are, in fact, compressed melanoma cells and not nevus cells.

Melanomas also may arise from primary acquired melanosis or de novo.

Regional lymph nodes: The regional lymph nodes are parotid, preauricular, submandibular, and cervical.

For pN (see Staging), histologic examination of a regional lymphadenectomy specimen ordinarily includes 6 or more regional lymph nodes.

Metastatic sites: In addition to spread by lymphatics and the bloodstream, direct extension to the eyeball and orbit occurs.

Frequency:

In the US: Primary malignant melanoma of the conjunctiva is much less common than intraocular or skin melanomas. Malignant melanoma of the conjunctiva accounts for only 2% of all ocular malignancies.

Internationally: Denmark: Incidence of primary acquired melanosis (PAM) with atypia or with malignant melanoma of the conjunctiva was estimated to be 0.052 cases a year per 100,000.
Sweden: Only 2 new cases of primary malignant melanoma of the conjunctiva were diagnosed in 1987.

Mortality/Morbidity: The overall tumor-related mortality rate for conjunctival melanoma is 25-26%. This rate increases to 40-44% if the tumor arose from PAM with an intraepithelial pagetoid growth pattern. This tumor tends to spread first to the parotid or submandibular nodes.

Tumor thickness, mixed cell type, and lymphatic invasion on histologic examination were found to increase the death rate (3-4 times).

Other poor prognostic features, outlined by Jakobiec and associates, include tumor in unfavorable locations (caruncle, palpebral conjunctiva, or fornical conjunctiva), moderate-to-severe atypia, a paucity of small polyhedral cells in the tumor, invasion of deeper ocular tissues, greater than 5 mitotic figures per 10 high-power fields, and lack of an inflammatory response induced by the tumor.

Race: This condition occurs predominantly in whites and rarely is seen in blacks.

Sex: No clear sex predilection has been established.

Age: Typically, conjunctival melanoma occurs in patients in their early 50s. It rarely is seen in people younger than 20 years. In 1999, Strempel reported 3 cases of conjunctival malignant melanoma in children.