Melanocytoma of the Conjunctiva: Clinicopathologic Features of Three Cases

Two Cases of Giant Melanocytoma (Hyperpigmented Magnocellular Nevus)

Melanocytoma or hyperpigmented magnocellular nevus is a variant of melanocytic nevus that is most commonly seen in the optic nerve, but has also been reported to occur in the iris, ciliary body, choroid, sclera, and conjunctiva. We present two cases of giant uveal melanocytoma with histopathology. The first case occurred in a 10-year-old girl who presented with decreased vision in the right eye and a mushroom-shaped pigmented choroidal lesion measuring 15.5 mm in apical height. The lesion was abutting the lens but not causing a cataract. This was diagnosed as a choroidal melanocytoma on open scleral window biopsy. The second case was in a 68-year-old lady, referred for a left nasal pigmented choroidal lesion measuring 8 mm in apical height and having a mushroom configuration. The lesion grew to 8.6 mm in height and was complicated by a vitreous hemorrhage and rhegmatogenous retinal detachment and was treated with iodine-125 plaque brachytherapy. Subsequently, the treated eye became a painful phthisical eye and was enucleated. Histopathology confirmed melanocytoma with extrascleral extension but without malignant transformation. Features of melanocytoma and other very large cases reported in the literature are discussed.

Combined deep penetrating nevi of the conjunctiva are relatively common lesions characterised by BRAFV600E mutation and activation of the beta catenin pathway: a clinicopathological analysis of 34 lesions

BACKGROUND

Deep penetrating nevus (DPN) is not a widely recognised lesion on the conjunctiva and only a few cases consistent with combined DPN have been reported.

METHODS

A review of all excised and histopathologically diagnosed conjunctival melanocytic lesions between 2003 and 2018 was performed in order to identify melanocytic nevi morphologically consistent with DPN.

RESULTS

Thirty-four DPN were identified among 361 histopathologically examined conjunctival nevi (9.4%), including 33 (97%) combined with a common nevus and 1 (3%) pure DPN. The patients' age ranged from 7 to 51 years (median, 22 years). Clinically, 21 of 29 (72%) lesions with available data were darkly pigmented, and an increase in size and/or pigmentation was noted in 13 of 18 (72%) lesions with known history. All 24 lesions in which an immunohistochemical analysis was possible were diffusely positive for BRAFV600E (in DPN and common nevus components) and showed a diffuse nuclear positivity for beta catenin and cyclin D1 in the DPN component. None of the 21 lesions with available follow-up data recurred during a follow-up period from 0.3 to 16.3 years (median, 7.5 years).

CONCLUSIONS

DPN of the conjunctiva is a relatively common lesion and usually presents as a combined nevus. Genetically, DPN of the conjunctiva are characterised by a combination of BRAFV600E mutation and activation of the beta catenin pathway. Recognition of DPN of the conjunctiva is important in order not to overdiagnose it as a melanoma, and to explain its potential atypical clinical features. DPN of the conjunctiva seems to be a benign lesion.