Immunohistochemical study of pleomorphic adenoma of lacrimal gland.

Immunohistochemical examinations of lacrimal gland specimens were carried out with monoclonal antibodies to S-100 protein and glial fibrillary acidic protein (GFAP) in 3 cases of normal tissue, 2 cases of hypertrophy and 3 cases of pleomorphic adenoma of the lacrimal gland. In specimens of normal lacrimal gland tissue, S-100 protein was identified in myoepithelial cells and ductal epithelia, but GFAP was not identified in any part of the gland. In specimens of lacrimal gland hypertrophy, the findings were identical. In pleomorphic adenoma of the lacrimal gland, asteroid cells in the myxoid and/or chondroid areas were strongly stained by antibodies to both S-100 protein and GFAP. In the solid areas of pleomorphic adenoma specimens, 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 that GFAP could be a tumor-associated antigen. These findings agreed with recent immunohistochemical findings in pleomorphic adenoma of the salivary gland. It was speculated that pleomorphic adenoma of the lacrimal gland could cause mesenchymal metaplasia of the myoepithelial cells, as happens in pleomorphic adenoma of the salivary gland.