ABCDE of a pigmented caruncular lesion
A 59-year-old Caucasian woman was referred for a pigmented lesion in the left medial canthus that was present for approximately 2 years. The lesion had become darker with central elevation in the past 6 months. A photograph shows areas of dark pigment extending over the medial one-third of the upper and lower lids as well as the caruncle. She is one package a day smoker. But she had no known medical problems and had no surgery in the past.

The vision was 20/20 in each eye and the rest of the ocular exam was normal. Histopathological analysis reveals a malignant process harboring atypical pigmented cells with high nuclei to cytoplasmic ratio encompassing the whole thickness of the epithelium. Subepithelial clusters of heavily pigmented cells and transitioning to nevoid cells with nuclear pseudo-inclusion and then to individual fusiform cells deeper in the dermis were observed; a nesting-maturation pattern characteristic to nevi. The immunohistochemical panel shows diffuse MART1-MelanA positivity, whereas HMB-45 revealed superficial positivity and low immunoreactivity in the deep portion of the lesion, confirming the presence of a subepithelial nevus. The malignant cells, confined to the epithelium, were also positive for MART1-MelanA and HMB-45.

Malignant melanoma or melanoma in situ of the eyelid or canthus is a rare disease that represents less than 1% of all skin melanomas. To evaluate pigmented lesions of the eyelid, the ABCDE guidelines for skin melanocytic lesions are applicable (A: asymmetry, B: Border, C: color, D: diameter, E: evolution). A biopsy is required for the suspicious lesions. In this case, melanoma was diagnosed, and the lesions are suspected to have arisen from a preexisting nevus that became darker and thicker (ABCDE). The patient will require wide excision of the lesion with clear margins either with frozen section or Mohs micrographic surgery followed by eyelid reconstruction. In this particular case, Mohs micrographic surgery was the chosen approach. A close follow-up is necessary to detect any recurrence of the lesion.