A 28-year-old man presented with an orbital tumour that was localized by computérized tomography to the fossa of the right lacrimal gland. A benign mixed tumour of the lacrimal gland was the clinical diagnosis, but lateral orbitotomy revealed a subperiosteal cystic mass in the lacrimal gland fossa that extended superiorly and medially into the frontal sinus. Light microscopic examination showed a cyst lined by nonkeratinized stratified squamous epithelium with occasional goblet cells; blood products were present in the lumen, and a chronic inflammatory cell infiltrate was noted in the subepithelial tissue. The possible origins of this mucosal tissue are discussed.