Oncocytic lesions of the ocular adnexa: A review of the histopathology with a brief discussion of the pathogenesis.

Oncocytic lesions may be metaplastic, hyperplastic, or neoplastic and occur in a variety of tissues, including those of the ocular adnexa. Oncocytes are enlarged epithelial cells with abundant eosinophilic granules in the cytoplasm, which represent large mitochondria with distorted cristae. The causes of oncocytic lesions remain uncertain, although in some sites such as the lacrimal sac, chronic inflammation may be a factor. Oncocytic neoplasms in all adnexal sites are generally benign (oncocytoma/oncocytic adenoma) and oncocytic adenocarcinomas are uncommon. Research into oncocytic neoplasms, particularly of the kidney and thyroid, has shed some light on the complicated genomic and metabolic changes that are associated with mitochondrial dysfunction in such neoplasms. The major driver event is mutation of mitochondrial DNA-encoding subunits of complex I in the respiratory chain. The subsequent metabolic events may promote tumorigenesis and inhibit malignant transformation. This review discusses the histopathology and histogenesis of two examples of oncocytoma in the ocular adnexa and presents a simplified synopsis of the genomic and metabolic changes that are significant in the pathogenesis of these neoplasms.