Myoepithelioma of the lacrimal gland: Report of a case with potentially malignant transformation

Myoepithelioma of the lacrimal gland is extremely rare and only four cases, one of which was malignant, have been reported in detail. The present repo rt describes a case of lacrimal gland myoepithelioma in a Japanese male wit h histological features suggestive of potentially malignant trans-formation . The excised tumor consisted of two components, a central nodular componen t and a peripheral component surrounding the former. These components were separated by a fibrous tissue, Microscopically, both components were compri sed almost entirely of spindle-shaped cells, but with some epithelioid cell s containing glycogen granules. Extracellular spaces in the peripheral comp onent were filled with eosinophilic materials with the occasional crystallo id structures, which were immunoreactive for collagen type I. Neoplastic ce lls were immunoreactive focally for vimentin and S-100, but negative for cy tokeratins, epithelial membrane antigen, muscle actin, smooth muscle actin, desmin, myosin, and glial fibrillary acidic protein. The neoplastic cells in the central component showed nuclear pleomorphism and atypia with a high er frequency of mitotic figures, and higher labelings of proliferation mark ers than those in the peripheral component. Neither invasion, necrosis, nor hemorrhage was observed in the tumor. From these findings we proposed a di agnosis of potentially malignant myoepithelioma.