Conjunctival pigmented lesions

The CMGs are guidelines on the diagnosis and management of a range of common and rare, but important, eye conditions that present with varying frequency in primary and first contact care.

Aetiology

Conjunctival pigmented lesions include a spectrum of benign, pre- malignant and malignant melanocytic conditions:

Melanosis

Hypermelanosis (i.e. melanin overproduction by normal melanocytes)
- racial melanosis
- secondary melanosis (Addison’s disease; conjunctival lesions)
Primary acquired melanosis (PAM), also known as conjunctival melanocytic intraepithelial neoplasia (C-MIN)
- with or without ‘atypia’ (cellular structural abnormalities), graded according to cytomorphology, melanocytic density and spread to superficial layers of epithelium. Severe disease amounts to Melanoma in situ (i.e., confined to epithelium)
Congenital melanocytosis
- hyperpigmentation of episclera as a result of an overpopulation of melanocytes, also occurring in uvea and skin (i.e., Naevus of Ota). Predisposes to melanoma.

Naevus (most common conjunctival pigmented lesion)

the most common conjunctival pigmented lesion: 52% of ocular pigmented lesions
congenital or acquired
cluster of naevus cells in the conjunctival epithelium, usually extending to substantia propria. Cysts are often present.

Melanoma

rare malignant tumour arising from naevus, PAM or de novo: 3-5% of ocular malignancies, incidence 0.2-0.8 per million in Caucasian populations
may arise in both sun-exposed and non-sun-exposed parts of the conjunctiva
metastasises to regional lymph nodes and systemically, especially if involving caruncle and/or non-bulbar conjunctiva

Systemic disorders and drugs linked rarely with conjunctival pigmentation include:

Addison’s disease (adrenal gland deficiency)
alcaptonuria (congenital enzyme deficiency)
drugs (chlorpromazine, topical epinephrine, etc)

Some of these conditions are illustrated at: http://www.eyecancer.com/research/image-gallery/3/conjunctival-tumors

Predisposing factors

Epithelial melanosis is common in dark-skinned ethnicities.

PAM typically affects older white-skinned patients (rarely in darkskinned).

Melanoma is more common with fair skin and blue eyes, extremely rare in dark-skinned races.

Presentation peaks in mid-fifties

Symptoms

Asymptomatic except for cosmetic concern

Signs

Ethnic melanosis

Bilateral, asymmetrical, flat, intra-epithelial (moves freely over sclera), patchy, brown pigmentation, most prominent in palpebral aperture especially at limbus or where anterior ciliary arteries perforate the sclera, develops in early years (static by adulthood)

C-MIN/PAM

Unilateral, any part of conjunctiva (including tarsal or forniceal), flat, intraepithelial (moves freely over sclera), single or multiple, indistinct areas, light to dark brown, no cystic spaces, often extensive, can be stable or may change (enlarge, shrink, darken or lighten)

Congenital melanocytosis

ocular
- Multifocal, slate-grey or blue grey, sub-epithelial (does not move freely over sclera)
dermal
- Mottled, blue to purple, discolouration of skin around the eye

Naevus

Solitary, sharply-demarcated, flat or slightly-elevated, intra-epithelial (moves freely over sclera). Confined to interpalpebral zone (very rare in palpebral or forniceal conjunctiva), most commonly adjacent to but not touching the limbus (less frequently at plica, caruncle, lid margin). NB: a pigmented lesion that straddles the peripheral cornea is highly suspicious and should be assumed to be a malignant melanoma. Presents in second or third decade when naevus becomes pigmented. Colour ranges from deep brown through pink to barely perceptible pigment. Often contains cystic spaces. Very rarely vascularised or inflamed

Melanoma

Nodular, well-vascularised mass with large conjunctival feeder vessels, fixed to underlying sclera (assess the degree of tethering, under topical anaesthesia). May be pigmented or non-pigmented (amelanotic), and nodular, diffuse or mixed. Clinicopathological features significantly associated with a poor prognosis are extrabulbar location, involvement of adjacent tissue structures, tumour thickness exceeding 2 mm and local tumour recurrence

Differential diagnosis

Conjunctival intraepithelial squamous neoplasia (i.e. carcinoma in situ) can resemble an amelanotic melanoma

Blue naevus: a rare congenital deeply pigmented melanocytic lesion which can resemble PAM or melanoma

Management by optometrist

Practitioners should recognise their limitations and where necessary seek further advice or refer the patient elsewhere

GRADE Level of evidence and strength of recommendation always relates to the statement(s) immediately above