Progressive changes in congenital hypertrophy of the retinal pigment epithelium.

A disc-shaped flat, heavily pigmented tumour (5 mm diameter) was discovered at the retinal periphery in a glutaraldehyde fixed eye which was enucleated in treatment of a peripapillary melanoma in a 60 year old man. The macroscopic appearances of the peripheral lesion were identical to those described in clinical reports as "Congenital Hypertrophy of the RPE". By light microscopy and transmission electron microscopy the hamartoma consisted of a hypertrophic and hyperplastic layer of RPE cells beneath an atrophic outer retina. The hyperplastic RPE cells did not contain lipofuscin and the content and size of the abnormal melanin granules increased towards the retinal aspect. The cells were linked by complex process interdigitations and attachments; the intercellular spaces contained basement membrane material and 100 nm banded collagen. Large vacuolar structures were prominent in the cells adjacent to the normal choriocapillaris. In the RPE cells at the periphery there was an excess lipofuscin and here there were recognisable outer segments. The morphological pattern suggested that this lesion should be considered as a congenital hypertrophy of the RPE which has progressed to focal segmental hyperplasia and focal atrophy.