PATHOLOGY OF MUCOUS AND SALIVARY GLAND TUMOURS IN THE LACRIMAL GLAND AND THE RELATION TO EXTRA-ORBITAL MUCOUS AND SALIVARY GLAND TUMOURS (Studies on Orbital Tumours 3)
The mixed lacrimal gland tumors were formerly regarded, from a histologic and biologic point of view, as polymorphic tumors. It is now shown that the genesis of these tumors is purely ectodermal, and that the so-called "mesen-chymal" elements (fibrils, hyaline cartilage, etc.) are ectodermal products of epithelial cells which have undergone metaplasia. There is a close resemblance between these tumors and the mucous and salivary gland tumors which occur in the salivary glands and in the mucous membrane of the nose and paranasal sinuses. There are 2 main histopathologic types: (1) the fibro-myxo-epithelioma, which is usually benign; (2) the basalioma, so-called because of its close histologic resemblance to the basal cell carcinoma of skin. This may occur in 2 forms, the cystic type (cylindroma) and the solid type. The basalioma is usually highly malignant, but it is less common than type (1). The cylindroma is radio-sensitive. Following adequate surgical removal the tumors of the nose and paranasal sinuses have a much better prognosis than those which develop in the large salivary glands, especially the parotid gland, and the lacrimal gland. The lacrimal and parotid glands are the only pure serous tubulo-alveolar glands in the body and this anatomical similarity may explain their pathologic resemblance.