[Immunohistochemical study of pleomorphic adenoma of the lacrimal gland].

We performed immunohistochemical examinations in 1 hypertrophy and 3 pleomorphic adenomas of the lacrimal glands with monoclonal antibodies to S-100 protein and GFAP (glial fibrillary acidic protein). It was thought that hypertrophy of the lacrimal gland would be cytological equivalent to normal lacrimal gland tissue because of the lack of cytological atypia except when accompanied by lymphoid infiltration. In hypertrophy of lacrimal gland, S-100 protein was identified in myoepithelial cells and parts of the ductal epithelia, but GFAP was not identified in any part. In pleomorphic adenomas of lacrimal glands, asteroid cells of myxoid and/or chondroid areas were strongly stained with both antibodies to S-100 protein and GFAP. In solid areas of pleomorphic adenomas, S-100 protein-positive fusiform or round cells and GFAP-positive round cells were observed. It was thought that S-100 protein-positive cells could have originated from myoepithelial cells and GFAP could be a tumor-associated antigen. The results coincided with recent immunohistochemical findings of pleomorphic adenoma of the salivary gland. It was suspected that pleomorphic adenoma of lacrimal gland could develop from mesenchymal metaplasia of myoepithelial cells as in the case of pleomorphic adenoma of salivary gland.