A histopathologic study of the pigmented fundus lesions in familial adenomatous polyposis.

A postmortem examination of the eyes of a 61-year-old woman with familial adenomatous polyposis was performed using light microscopy and transmission and scanning electron microscopy. Numerous lesions of the retinal pigment epithelium (RPE) were identified, which had one of three basic configurations: a monolayer of hypertrophic cells, a mound of RPE cells interposed between the RPE basement membrane and the inner collagenous layer of Bruch's membrane, or a multilayered mound of hyperplastic cells. The presence of abnormal pigment granules in cells within the lesions and cells from areas of grossly normal RPE indicates a generalized defect in melanogenesis. Although the pigmented fundus lesions of familial adenomatous polyposis are often referred to clinically as congenital hypertrophy of the RPE, the prominent component of cellular hyperplasia more appropriately designates them as hamartomas of the RPE. Their development is likely the result of the same loss of regulatory control of cell growth and replication that gives rise to the multiple colorectal polyps and soft tissue tumors that characterize this condition.