Adenoid cystic carcinoma (AdCC) is the most frequent malignant neoplasm of the lacrimal glands. Like its salivary gland counterpart, lacrimal AdCC can rarely undergo high-grade transformation ("dedifferentiation"). We herein report the clinical, radiographic and microscopic findings of a lacrimal gland AdCC with high grade transformation, occurring in a 39-year-old female patient. In contrast to salivary gland AdCC with high-grade transformation, which usually shows a high grade component with "ductal" differentiation, in the case presented, the "dedifferentiated" component showed morphologic and immunohistochemical features of myoepithelial differentiation.