Metastasizing Pleomorphic Adenoma of the Salivary Gland Involving the Sternum: A Case Report

Abstract: BACKGROUND: The acinar-ductal units of the three pairs of main salivary glands (submandibular, sublingual, and parotid) and small salivary glands are encircled by myoepithelial cells, which are functionally altered epithelial cells that produce extracellular matrix. The majority of salivary gland tumors are benign; large glands account for 70% of cases, while small glands account for 25%. Salivary gland tumors make up 2 to 6.5% of all head and neck neoplasms. Tumors in the salivary glands can be cancerous at different rates—most often in the sublingual gland, less so in the submandibular gland, and least commonly in the parotid gland. Among adults, pleomorphic adenoma is the most commonly diagnosed salivary gland tumor, which is often a benign with a well-defined circumference and a modest growth rate. Despite being malignant, metastatic pleomorphic adenoma (MPA) shares identical histological features with benign pleomorphic adenoma (PA). This report details a case of pleomorphic adenoma of the salivary gland exhibiting metastasis to the sternum in an geriatric patient.