Mesectodermal leiomyoma of the ciliary body: new evidence for neural crest origin.

An 8-year-old white boy had a mass of the ciliary body in his left eye. Both the translucent characteristics and the magnetic resonance imaging findings suggested that this lesion was cystic. Fluid aspiration biopsy and iridocyclectomy were performed. By light microscopy the neoplasm showed the characteristic appearance of a neuroid tumor; however, on electron microscopic examination, the tumor exhibited characteristic features of a smooth muscle neoplasm and was diagnosed as a mesectodermal leiomyoma. Observation of melanin granules in scattered tumor cells further confirmed that the tumor had the same origin as uveal melanocytes, which also derive from the neural crest.