Leiomyoma of the iris

Leiomyomata of the iris are infrequent (Erdbrink and Harbert, I955), and represent, according to the literature, between 2-3 and I4 per cent. of all iris tumours. They have been reported only in white subjects aged between Io and 77 years, females being more frequently affected. They involve most commonly the lower half of the iris, more often on the temporal side, and may arise from either the sphincter or the dilator muscle. Despite the neuroectodermal origin of the iris muscles, the tumour is a typical leiomyoma, showing histological features similar to those originating in the mesodermal smooth muscles. They appear as a well circumscribed, slightly elevated, greyish-white or pink, xascularized mass, hyphaema being not unusual. The pupillary reflexes are not usually affected and ectropion uveae is frequent. Clinical symptoms are absent (Ferrer, I949) and vision is not impaired unless hyphaema, cataract, or secondary glaucoma develops. The clinical diagnosis is difficult because in a high percentage of cases it is impossible to differentiate an iris leiomyoma from a lightly-pigmented malignant melanoma (DukeElder, I966). The treatment of choice is total excision of the tumour when it is well limited, but if the growth is active, with diffuse invasion of the iris and/or extension to the anterior chamber angle, the eye should be enucleated. Prognosis is good if the tumour is removed before invasion of the neighbouring structures has occurred. No metastases have been reported but there may be local recurrence when the tumour is not totally excised. Histologically (Brown, Kellenberger, Hudson, and Matthews, I957; Nordmann and Brini, I 962; Ashton and Wybar, I 966; Cullmann, I 968), iris leiomyomata show elongated interlacing spindle cells, with oval, sometimes palisaded nuclei, and eosinophilic cytoplasm containing numerous myoglial fibrils best demonstrated with Mallory phosphotungstic-acid haematoxylin, Masson's trichrome stain, and gold impregnation.