Mesectodermal leiomyoma of the ciliary body: report of a case and review of the literature.

Mesectodermal leiomyoma of the ciliary body is a rare benign tumor with double (muscular and neural) differentiation. This neoplasm is considered to originate from the ciliary body smooth muscle, a neural crest derivative. We report a case of mesectodermal leiomyoma of the right eye occurring in a 53-year-old woman, who presented with significant decrease of visual acuity. A malignant melanoma was highly suspected on clinical evaluation, and the globe was enucleated. The tumor measured 1.2cm in greatest dimension, and consisted of spindle and ovoid cells with abundant fibrillary cytoplasmic processes. Immunohistochemical stains revealed positivity for smooth muscle actin, caldesmon, neuron-specific enolase, and CD56 antigen. A review of the 23 cases thus far reported in the literature shows a striking predilection for women, as well as significant difficulties in differentiating this tumor from malignant melanoma on clinical grounds.