Focal congenital anomalies of the retinal pigment epithelium

The terms, 'hamartoma', 'choristoma', 'phacoma' (mother-spot), and 'naevus', are used to describe benign developmental tumours or placoid lesions. Stedman's Medical Dictionary defines a hamartoma as: 'A focal malformation that resembles a neoplasm grossly and even microscopically, but results from faulty development in an organ; it is composed of an abnormal mixture of tissue elements, or an abnormal proportion of a single element, normally present in that site, which develop and grow at virtually the same rate as normal components, and are not likely to result in compression of the adjacent tissue (in contrast to neoplastic tissue).'1 A choristoma is defined as 'a mass formed by maldevelopment of tissue of a type not normally found at that site.' Phacoma is defined as, 6 a hamartoma found in phacomatosis,' a group of hereditary diseases characterised by hamartomas of multiple tissues. A naevus is a, 'birthmark; a circumscribed malformation of the skin, especially if coloured by hyperpigmentation or increased vascularity; it may be predominantly epidermal, adnexal, melanocytic, vascular, or mesodermal, or a localised overgrowth of melanin-forming cells arising in the skin early in life.' Ophthalmologists have adopted the term to refer to developmental melanocytic lesions of the uveal tract, but heretofore have not used it to describe developmental melanocytic, glial, or vascular lesions of the retina. The purpose of this report is to summarise the author's observations and concepts concerning focal lesions that probably are developmental tumours and placoid lesions composed of either entirely or in part retinal pigment epithelium (RPE). Two of the lesions are tumefactions and may properly be termed 'hamartomas' (Table I). Four of the lesions are placoid and might better be described as naevi. Two are composed of hypertrophied RPE cells engorged with melanin granules, one is presumed to be hypertrophied RPE cells filled with a white pigment of unknown nature and one is composed of RPE cells containing no pigment. Three are widely recognised, three others are not.