Light and electron microscopic study on dermoid cyst appeared under the mucous membrane arround the vallate papilla of the rat

Dermoid cyst appeared under the mucous membrane around the vallate papilla of the rat's tongue was examined by light and electron microscope. The cyst was lined with stratified squamous epithelium and filled with keratin. Sebaceous gland rich in fat droplets was found near the cyst. Epithelial cells of the cyst were combined with each other by the well developed desmosomes and with the basal lamina by the half-desmosomes. The structures of the intracellular granules, such as the membrane-coating granules and keratohyalin granules, and of the surface coat of the keratinizing epithelial cells, were identical with those of the normal epidermis. It seemed that the occurrence of the dermoid cyst in this region was very rare.