Primary Conjunctival Pigmented Basal Cell Carcinoma with Increased Numbers of Intra-Tumour Melanocytes, Mimicking Melanoma: A Case Report and Review of the Literature

Abstract

Basal cell carcinoma (BCC) is a common eyelid skin tumour that can arise very rarely from the conjunctiva.• The pigmented variant of BCC accounts for 6% of skin BCCs but has never been reported in the conjunctiva. Novel Insights• This is the first report of a pigmented BCC of the conjunctiva, mimicking a conjunctival melanoma.• The pigmented BCC showed prominent melanocyte hyperplasia, melanophages and tumour cell cytoplasmic melanin. • Pigmented BCC should be considered in the differential diagnosis of pigmented, non-melanocytic tumours of the conjunctiva. AbstractA 60-year-old, South-Asian male patient presented with a dark brown lesion on his left conjunctiva surface near the limbus for 2 years. Examination showed a globular, dark brown-coloured mass near the temporal limbus at 4 to 5 o'clock position, measuring 3 × 3 × 2 mm. There were a few scattered flat pigmented lesions near the mass and also a few prominent vessels. The mass underwent wide local excision, with a clear margin, followed by double freeze cryotherapy of the conjunctival margins along with the application of Mitomycin C. The bare sclera was covered by amniotic membrane. Histology surprisingly revealed a nodular basal cell carcinoma (BCC) containing melanin. The melanin was present in the tumour cell cytoplasm, within melanophages and within dendritic, Melan A-positive melanocytes. The BCC was immunohistochemically positive for BerEP4 and negative for EMA. The clinically observed smaller nodules flanking the main pigmented BCC corresponded histologically to pigmented superficial growth pattern BCC connected to the under surface of the conjunctival epithelium. This is the first report of a pigmented BCC of the conjunctiva, mimicking a conjunctival melanoma. Pigmented BCC should be considered in the differential diagnosis of pigmented tumours of the conjunctiva.

Primary Basal Cell Carcinoma of the Conjunctiva

“…It is far more common to observe eyelid BCC with secondary involvement of the conjunctiva [1]. In the literature, only five reports of primary conjunctival BCC have been illustrated [3][4][5][6][7].…”

“…Of the five primary conjunctival BCC reported in the literature, male cases (n = 4) were more common than female cases (n = 1) [3][4][5][6][7]. Patient ages ranged from 60 to 82 years.…”

“…Several mechanisms have been postulated. Metaplasia of the conjunctival epithelium secondary to ultraviolet damage or development of BCC from a dermoid choristoma has been suggested in causing BCC in the conjunctiva [ 7 ]. Furthermore, it may be metastasized from adjacent skin cancer [ 7 ].…”

“…Metaplasia of the conjunctival epithelium secondary to ultraviolet damage or development of BCC from a dermoid choristoma has been suggested in causing BCC in the conjunctiva [ 7 ]. Furthermore, it may be metastasized from adjacent skin cancer [ 7 ]. Nevertheless, prolonged sun exposure can be a contributing factor in our patient who revealed no systemic or skin malignancies.…”

“…Aftab and Percival reported a primary BCC of the conjunctiva resembling a papilloma clinically [ 3 ]. In one report, BCC appeared as a dark brown pigmented mass near the limbus and was thought to be a conjunctival melanoma [ 7 ]. Our patient had a unilateral vascularized pigmented limbal mass located in the sun-exposed interpalpebral fissure laterally, clinically mimicking an atypical OSSN.…”