From the Guidelines
Pleomorphic adenoma originates from the salivary gland tissue, most commonly in the parotid gland. This is based on the most recent evidence from 2023, which states that the majority, approximately 70% to 80%, of these tumors are benign, with the most common benign tumor being pleomorphic adenoma (60%-70%) and that they occur most frequently in the parotid gland, followed by the submandibular gland, and lastly the sublingual gland 1.
Key Points
- The parotid gland is the most common site of origin for pleomorphic adenoma, accounting for approximately 70-80% of cases 1.
- The tumor develops from the epithelial and myoepithelial cells of the salivary gland ducts, resulting in a mixed histological appearance containing both epithelial and mesenchymal-like components.
- While the exact cause of pleomorphic adenoma remains unclear, certain genetic alterations, particularly involving the PLAG1 and HMGA2 genes, have been implicated in its development.
- Treatment generally involves complete surgical excision with a margin of normal tissue to prevent recurrence, as these tumors have a small risk of malignant transformation if left untreated for many years.
Clinical Presentation
- Pleomorphic adenoma typically presents as a slow-growing, painless, firm mass that may have been present for months to years before diagnosis.
- Patients may experience weakness of the facial muscles if there is perineural spread of disease.
- The risk of malignancy is inversely proportional to the size of the gland, with the risk of cancer being greater in a sublingual gland lesion as opposed to a lesion in the parotid gland 1.
From the Research
Origin of Pleomorphic Adenoma
- Pleomorphic adenoma originates from the salivary glands, which include the major and minor salivary glands 2.
- The majority of pleomorphic adenomas (about 85%) are found in the parotid gland, while 10% occur in the minor salivary glands and 5% in the submandibular gland 2.
- The minor salivary glands can be found in various locations, including the palate, lips, cheeks, throat, floor of the mouth, tongue, tonsil, pharynx, retromolar area, and nasal cavity 3, 4, 5.
Specific Locations of Pleomorphic Adenoma
- The parotid gland is the most common location for pleomorphic adenoma, accounting for about 90% of cases 4, 5, 6.
- The minor salivary glands, such as those found in the cheek, are less common locations for pleomorphic adenoma 3, 4.
- Other rare locations for pleomorphic adenoma include the masticator space, which has been reported in only one case in the English language literature 5.