Immunohistologic properties of benign and malignant mixed tumor of the lacrimal gland. We studied the immunohistopathologic features of normal lacrimal gland, benign mixed tumor, and malignant mixed tumor of the lacrimal gland. Primary antisera were to keratin, muscle-specific actin, vimentin, and glial fibrillary acid protein. Keratin stained in occasional myoepithelial cells in normal gland, ductal epithelium in normal gland and the tumors, and occasional stromal epithelioid cells in the tumors. Muscle-specific actin stained in myoepithelium and vascular smooth muscle in normal gland and the tumors, and occasional spindle-shaped and clusters of stromal cells in the tumors. Vimentin staining was nonspecific. Glial fibrillary acid protein stained in occasional myoepithelial cells in normal gland and polyhedral stromal cells in benign mixed tumor. Our findings indicate that ductal epithelium develops into the epithelial component, and some cells in the stroma and myoepithelium develop into some cells in the stroma of benign and malignant mixed tumor of the lacrimal gland. 