Malignant melanocytic lesions in clinically suspected pterygium

To determine the prevalence and clinicopathological features of malignant melanocytic lesions in specimens clinically diagnosed as pterygia.

This retrospective study analysed all conjunctival specimens submitted with the clinical diagnosis 'pterygium' to the ophthalmic pathology laboratory of the Eye Center, University of Freiburg, Germany, between August 1999 and August 2024. Specimens that unexpectedly revealed a histopathological diagnosis of malignant melanocytic lesions were further reviewed for their clinical and pathological characteristics.

Among 2298 clinically presumed pterygia, seven specimens (0.30%) harboured a malignant melanocytic lesion: four (0.17%) were invasive conjunctival melanomas and three (0.13%) were high-grade conjunctival melanocytic intraepithelial lesions (C-MIL). Three of four melanomas were amelanotic or hypomelanotic (75%) or exhibited atypical temporal localisation (75%).

Malignant melanocytic lesions, though rare, may arise within or mimic pterygia. Their often amelanotic presentation can complicate clinical recognition. Routine histopathological evaluation of all excised pterygia is therefore essential to detect unexpected malignancies as conjunctival melanoma C-MIL.