Sector hamartoma of the iris

A 15-year old girl with a jet black-pigmented lesion on the anterior surface of the upper nasal quadrant of her iris was followed up for 12 years, during which interval growth of the lesion was documented. Histopathological evaluation of the excised segment of the iris revealed a pigment epithelial proliferation originating from posterior pigment epithelium. Additionally, there was a band of spindle shaped smooth muscle cells in the posterior stroma and a zone of plump melanocytes in the anterior stroma beneath the proliferating pigment epithelial cells. This combination of abnormalities is thought to represent a benign hamartomatous maldevelopment of the involved sector of the iris rather than a true neoplasm. Such an elaborate dysgenesis is unlike the more modest melanocytic hamartomas of the iris associated with the phakomatoses.