Focal aggregates of normal or near normal uveal melanocytes (FANNUMs) in the choroid: a distinct clinical and histopathological entity?

PURPOSE: To define, describe, and illustrate a previously unreported category of discrete melanotic choroidal melanocytic lesion. METHODS: Prospective ophthalmoscopic study of the ocular fundi of 79 light-skinned persons 50 years of age or older not referred for any evident fundus lesion, with detection of all evident discrete melanotic choroidal lesions > 0.3 mm in largest basal diameter. RESULTS: One or more discrete dark-brown to gray choroidal lesions > 0.3 mm in largest basal diameter were detected in 27 of the 79 evaluated subjects (34.2%). All but four of the detected lesions were “flat” by both ophthalmoscopy and ultrasonography. A single flat lesion was present in one eye of 14 subjects whose fellow eye was normal, 2 or more flat lesions were evident in one eye of 5 subjects whose other eye was normal, and one or more lesions were evident in both eyes of 6 subjects. CONCLUSION: While some of the discrete small, flat melanocytic choroidal lesions detected in this study might have been choroidal nevi, the author hypothesizes that an indeterminate proportion of them may have been focal aggregates of normal or near normal uveal melanocytes (FANNUMs).