Clinical and immunohistopathological study of conjunctival melanocytic lesions in pediatric and adolescent patients. A case series

Background: Conjunctival pigmented neoplasia can be benign, premalignant or malignant tumors. Our study aims to establish the epidemiological, gross morphological and immunohistopathological features of the conjunctival pigmented lesions in pediatric and adolescent patients (<18 years), to establish an accurate diagnosis. Patients, Material and Methods: This is a retrospective case series study conducted within two Ophthalmology Clinics from Iaşi, Romania, on seven pediatric and adolescent patients. Using the Clinical Observation Chart and the Pathology Registers over a six-years period (January 2015–December 2021), we noted the patients’ demographic data, clinical data, and ophthalmological investigations of the lesion, as well as the type of their treatment. All histological sections stained with Hematoxylin–Eosin (HE) and with five antibodies [pan-cytokeratin (pan-CK) AE1/AE3, S100 protein, Melan A, human melanoma black 45 (HMB45), and Ki67] were re-examined by four pathologists for each case, to identify the type of the conjunctival lesion and its histological and immunohistochemical features. Results: The mean age of all patients was 10.28 years, and the female/male ratio was 1.3. Right eye was more often affected (71.42%). 71.42% of cases presented an elevated lesion, 57.14% of cases showed a lightly pigmented lesion, but 14.28% of cases exhibited a pink lesion and this feature described the inflamed juvenile conjunctival nevus. In all cases (100%) the conjunctival pigmented tumor was removed with safety margins. The microscopic examination revealed a compound melanocytic nevus in 57.14% cases, a junctional conjunctival nevus in 14.28% cases, an inflamed juvenile nevus in 14.28% cases, and a conjunctival melanoma arising from a pre-existing nevus in 14.28% cases. In all cases of nevi, the nevoid melanocytes showed strong immunopositivity for Melan A and S100 protein, variable and weak immunopositivity for HMB45, and a mean Ki67 labeling index of 1.71%. Conjunctival melanoma revealed strong immunopositivity of tumor cells for HMB45, Melan A and S100 protein, and a Ki67 labeling index of 20%. In all cases, the conjunctival epithelium showed strong immunopositivity for pan-CK AE1/AE3. All our cases (100%) had a favorable outcome after the surgical removal of the tumor. Conclusions: Any excision of a conjunctival pigmented lesion must be subject to a systematic immunohistopathological examination, and there is a set of antibodies (anti-HMB45 and anti-Ki67) that are useful for differential diagnosis between a conjunctival nevus and a conjunctival melanoma.