2020–2021 BCSC Basic and Clinical Science Course™

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2020–2021 BCSC Basic and Clinical Science Course™

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8 External Disease and Cornea

Chapter 12: Clinical Approach to Neoplastic Disorders of the Conjunctiva and Cornea

Tumors of Neuroectodermal Origin

Table 12-2 lists the ocular surface tumors that arise from melanocytes, nevus cells, and other neuroectodermal cells. Some pigmented lesions of the globe are normal. For example, a pigment spot of the sclera is a collection of melanocytes associated with an intrascleral nerve loop or perforating anterior ciliary vessel. The term melanosis refers to excessive pigmentation without an elevated mass that may be congenital (whether epithelial or subepithelial) or acquired (whether primary or secondary). Conjunctival pigmentation can also occur because of long-term exposure to epinephrine compounds, minocycline, silver, or mascara (see Chapter 6, Fig 6-20).

Cameron JD, Maltry AC. Melanocytic neoplasms of the conjunctiva. In: Mannis MJ, Holland EJ, eds. Cornea. Vol 1. 4th ed. Philadelphia: Elsevier; 2017:434–441.

Shields CL, Demirci H, Karatza E, Shields JA. Clinical survey of 1643 melanocytic and non-melanocytic conjunctival tumors. Ophthalmology. 2004;111(9):1747–1754.

Benign Pigmented Lesions

Ocular melanocytosis

Congenital melanosis of the episclera occurs in approximately 1 in every 2500 individuals and is more common in black, Hispanic, and Asian populations.

PATHOGENESIS

Ocular melanocytosis represents a focal proliferation of subepithelial melanocytes.

CLINICAL PRESENTATION

Patches of episcleral pigmentation appear slate gray through the normal conjunctiva (Fig 12-8) and are immobile and usually unilateral. Affected patients may have a diffuse nevus of the uvea, evident as increased pigmentation of the iris and choroid. In approximately 50% of patients with ocular melanocytosis, there is ipsilateral dermal melanocytosis and a proliferation of dermal melanocytes in the periocular skin of the first and second dermatomes of cranial nerve V. The combined ocular and cutaneous pigmentations are referred to as oculodermal melanocytosis (nevus of Ota). Approximately 5% of cases are bilateral. Table 12-3 compares the various pigmented lesions of the conjunctiva.

Table 12-2 Tumors and Related Conditions of Neuroectodermal Cells of the Ocular Surface

Figure 12-8 Episcleral pigmentation in a patient with congenital ocular melanocytosis.

(Courtesy of Kathryn Colby, MD, PhD.)

In 10% of patients with ocular melanocytosis, secondary glaucoma occurs in the affected eye. Malignant transformation is possible but rare and seems to occur only in patients with fair complexions. Malignant melanoma can develop in the skin, conjunctiva, uvea, or orbit. The lifetime risk of uveal melanoma in a patient with ocular melanocytosis is about 1 in 400—significantly greater than the approximate 6-per-million risk of the general population.

Table 12-3 Clinical Comparison of Conjunctival Pigmented Lesions

Nevus

Nevocellular nevi of the conjunctiva consist of nests or more diffuse infiltrations of benign melanocytes. They arise during the first or second decade of life. Conjunctival nevi are classified as junctional (confined to the epithelial–stromal junction); subepithelial, or stromal (confined to the stroma); or compound (combines junctional and stromal components). Pure intraepithelial nevi are rare except in children.

On histologic examination, nevi can occasionally be very difficult to differentiate from melanoma. Junctional nevi may be difficult to distinguish from primary acquired melanosis (see the section “Primary acquired melanosis” later in the chapter).

CLINICAL PRESENTATION

A nevus near the limbus is usually almost flat. Nevi appearing elsewhere on the bulbar conjunctiva, plica semilunaris, caruncle, or eyelid margin tend to be elevated. Pigmentation of conjunctival nevi is variable: they may be light tan to brown or amelanotic (15% of cases; Fig 12-9). A subepithelial nevus often has a cobblestone appearance.

Small epithelial inclusion cysts occur within approximately half of all conjunctival nevi, particularly the compound or subepithelial varieties. Secretion of mucin by goblet cells in the inclusion cysts can cause a nevus to enlarge, giving a false impression of malignant change. Cellular proliferation may induce secondary lymphocytic inflammation. Rapid enlargement can occur at puberty, giving rise to a clinical impression of conjunctival melanoma. An amelanotic, vascularized nevus, when inflamed, may resemble an angioma, or it may be misdiagnosed as chronic conjunctivitis. See Table 12-3 for a clinical comparison of the various pigmented lesions of the conjunctiva.

Figure 12-9 Amelanotic conjunctival nevus.

(Courtesy of Kathryn Colby, MD, PhD.)

Jakobiec FA, Sandhu H, Bhat P, Colby K. Bilateral conjunctival melanocytic nevi of simultaneous onset simulating conjunctivitis in a child. Cornea. 2010;29(8):937–940.

Shields CL, Fasiuddin AF, Mashayekhi A, Shields JA. Conjunctival nevi: clinical features and natural course in 410 consecutive patients. Arch Ophthalmol. 2004;122(2):167–175.

MANAGEMENT

Conjunctival nevi rarely become malignant and can be followed with an examination every 6–12 months that includes serial photography or detailed slit-lamp drawings incorporating dimensional measurements. Excisional biopsy should be performed on lesions that show suspicious change or growth. A biopsy should also be performed for pigmented lesions on the palpebral conjunctiva or cornea or in the fornix, as nevi are rare in these locations.

Complexion-associated melanosis

Complexion-associated melanosis (CAM; also called racial melanosis) is more commonly seen in individuals with darker complexions, but it occurs in all races (approximately 95% of blacks, 35% of Asians, 30% of Hispanics, and 5% of whites). CAM appears as flat, light- to dark-brown conjunctival patches with irregular margins that are most apparent at the limbus and less prominent as it extends into the fornix (Fig 12-10). The pigmentation can also involve the caruncle and palpebral conjunctiva as well as extend into the cornea with streaks or whorls (striate melanokeratosis). Histologic findings consist of hyperpigmentation of the conjunctival basal epithelial cells without atypia or hyperplasia. CAM is bilateral, fairly symmetric, and benign, with little risk of progression to melanoma. It is important to differentiate CAM from primary acquired melanosis (discussed in the following section), which seldom occurs in individuals with darker skin, is usually unilateral or highly asymmetric, and can transform to melanoma.

Shields JA, Shields CL. Conjunctival melanocytic lesions. In: Eyelid, Conjunctival, and Orbital Tumors: An Atlas and Textbook. 3rd ed. Philadelphia: Wolters Kluwer; 2016:307–348.

Figure 12-10 Complexion-associated melanosis in a patient with corneal arcus.

(Courtesy of James Chodosh, MD.)

Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.

8 External Disease and Cornea

Chapter 12: Clinical Approach to Neoplastic Disorders of the Conjunctiva and Cornea

Tumors of Neuroectodermal Origin

Benign Pigmented Lesions

Ocular melanocytosis

PATHOGENESIS

CLINICAL PRESENTATION

Table 12-2 Tumors and Related Conditions of Neuroectodermal Cells of the Ocular Surface

Figure 12-8 Episcleral pigmentation in a patient with congenital ocular melanocytosis.

Table 12-3 Clinical Comparison of Conjunctival Pigmented Lesions

Nevus

CLINICAL PRESENTATION

Figure 12-9 Amelanotic conjunctival nevus.

MANAGEMENT

Complexion-associated melanosis

Figure 12-10 Complexion-associated melanosis in a patient with corneal arcus.

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