What is a Pleomorphic Adenoma?

A pleomorphic adenoma is the most common form of benign tumor in the salivary glands. It is also called a mixed tumor, as its histologic or tissue origin comes from different cell types. The tumor is usually a hard, mobile and painless solitary mass which grows slowly over time.

Most of these types of tumors develop in the parotid gland, with fewer incidences occurring in the submandibular glands and in the minor salivary glands. Salivary glands are responsible for the production of saliva in the mouth. The parotid gland is the largest salivary gland located near the upper teeth and just below the ear. This gland produces half of daytime saliva through drainage tubes known as salivary ducts. It has two lobes, the superficial and the deep, separated by the facial nerve. Submandibular glands, on the other hand, are located just beneath the tongue, while the minor salivary glands outline the lips, mouth and throat.

A pleomorphic adenoma generally occurs in adults between 45 and 60 years old, and is diagnosed more often in females than in males. Factors associated with pleomorphic adenoma can include chain smoking and radiation exposure. Most often, however, it is due to the blockage of salivary ducts, which inhibits saliva drainage from the glands. There are many reported untreated cases of pleomorphic adenoma. Left untreated, the tumors can experience malignant changes due to recurrence. The cancerous transformation is known as a malignant mixed tumor or carcinoma ex pleomorphic adenoma.

Adenomas are commonly tested by fine needle aspiration (FNA). FNA is a histopathologic technique, which is widely used for its safety in diagnosing pleomorphic adenoma. The procedure is generally performed by a pathologist, a doctor specializing in the study of tissues to determine the cause of disease. The test is completed by withdrawing a sample of the tumor using a needle and syringe. The tissue samples are then processed in the laboratory and read by the pathologist. Computed tomography (CT) scans and magnetic resonance imaging (MRI) tests are also frequently used to determine a tumor's location and size.

Treatment for pleomorphic adenoma generally involves surgical resection, or removal of the part of an organ affected by the tumor. Resection of the benign tumor in the parotid gland is usually done through superficial parotidectomy, or removal of the superficial lobe of the parotid gland. A total parotidectomy, which is the removal of both lobes, is also often performed to prevent recurrence, but extreme care is needed as this surgery can cause facial nerve damage. Surgical excision, or complete removal of the tumor with the use of a scalpel, is mostly done for benign tumors in the minor salivary glands and submandibular glands.