Metastasizing pleomorphic adenoma presents intraorally: a case report and review of the literature.

Pleomorphic adenoma (PA), also known as mixed tumor, is the most common benign salivary gland neoplasm, characterized histologically by both epithelial and mesenchymal elements. Approximately 75% of PAs occur in the parotid gland, followed by the submandibular gland (15%) and minor glands of the palate and nasal septum (10%). Less common is the occurrence in the minor glands of the upper lip, cheek, floor of mouth, larynx, and trachea. Malignant mixed tumors encompassing the entities, carcinoma ex pleomorphic adenoma, carcinosarcoma, or metastatic pleomorphic adenoma (MPA), are rare and represent 2% to 6% of all salivary gland tumors. MPA is the least common subtype of maignant mixed tumors. By definition, the histologic features of MPA must be identical to those of the PA of the initial salivary gland site. The sites of MPA are similar to the anatomic metastatic sites of other malignant salivary gland tumors, and hematogenous spread of MPA is more common than lymphatic. Bone is the most common metastatic locaion for MPAs (45%), followed by the head and neck 43%), lung (36%), and, less often, lymph nodes, aranasal sinuses, the central nervous system, kideys, liver, or skin. We report the first, to our