Primary iris leiomyoma

Intraocular leiomyomas are uncommon and usually occur in the ciliary body. Primary leiomyoma of the iris is both rare and a difficult diagnosis to make, given melanocytic tumors are more common and may be amelanotic. The somewhat controversial diagnosis of iris leiomyoma requires further confirmation by immunohistochemistry and electron microscopy. Herein, we describe a 58-year-old man with a 2-mm round translucent pink lesion of the iris. The tumor was excised by sector iridectomy. Immunohistochemistry showed positivity for both smooth muscle actin and desmin and negativity for S-100, HMB45, SOX10, MelanA, CD31, CD34, and h-caldesmon. Epstein-Barr virus-associated smooth muscle tumor was excluded by chromogenic in situ hybridization-Epstein-Barr virus-encoded RNA. Ultrastructural analysis showed cytoplasmic myofilaments with focal fusiform densities and micropinocytotic vesicles. Our review of previous literature confirmed the unusual nature of this tumor. Primary iris leiomyoma should be considered in the differential of an amelanotic S-100-immunonegative iris tumor.