Unusual uveal tract tumor: mesectodermal leiomyoma of the ciliary body

Benign smooth muscle tumor, leiomyoma, can occur throughout the whole body, including the most common sites of the genitourinary and gastrointestinal tracts, less frequently in the skin, and rarely in the deep soft tissue or uveal tract. A 23-year-old Chinese woman presented with a 4 month history of a pigmented ciliary body mass in her left eye. The tumor's clinical appearance and ancillary data were initially consistent with malignant melanoma. However, instead of enucleation, sclerotomy with a tumor biopsy was performed because of the patient's young age and the possibility of benign tumors. Under light microscopy, tumor cells were short spindle- or ovoid-shaped with fine nuclear chromatin and fibrillary cytoplasmic processes resembling neural tissue. Although the tumor displayed neurogenic morphology, it showed strong reactivity for alpha-smooth muscle-specific actin and h-caldesmon, and was negative for neurogenic markers, except CD56, by immunohistochemistry. Primary mesectodermal leiomyoma of the ciliary body was diagnosed because of both the myogenic and neurogenic characteristics. The tumor biopsy or intraoperative frozen section is suggested for accurate pathological diagnosis before enucleation. In a review of the literature, only 14 cases have been reported. Seven cases (50%) were subjected to enucleation and eventually showed a benign mesectodermal leiomyoma. This case report provides novel expression of h-caldesmon and CD56 by the tumor cells of mesectodermal leiomyoma.