A pleomorphic adenoma is a benign, or noncancerous, tumor that develops in the salivary glands, which produce saliva and are located in and around your mouth and throat. It is the most common tumor to arise in these glands and is also known as a mixed tumor because it is composed of a diverse mix of different cell types.
The name “pleomorphic” refers to this variability in the shape and size of the tumor’s cells. While these growths are not cancerous, they have the potential to enlarge over time, making proper management and treatment important.
Symptoms and Common Locations
The most frequent sign of a pleomorphic adenoma is a slow-growing, firm, and mobile lump that is typically painless. Many individuals have the mass for several years before seeking a diagnosis. Symptoms depend on the tumor’s size and location, and as it grows, it can cause a noticeable change in the skin’s contour or feelings of pressure.
These tumors most often occur in the major salivary glands. The parotid gland, situated in the cheek area in front of the ear, is the most common site, accounting for about 85% of cases. The submandibular gland, located under the jaw, is the second most common location. They can also develop in the minor salivary glands found throughout the lining of the mouth and throat, including the palate.
When a pleomorphic adenoma grows in the deep portion of the parotid gland, it may present as a mass in the back of the throat. In less common locations, a tumor might lead to specific symptoms like difficulty swallowing, changes in speech, or nasal obstruction. While usually asymptomatic, a rapid increase in size or the onset of pain could indicate a change in the tumor’s nature.
Diagnosis Process
Diagnosing a pleomorphic adenoma begins with a medical history and a physical examination. A healthcare provider will assess the lump’s size, consistency, and mobility, while also checking for any associated symptoms in the head and neck region.
Imaging studies like computed tomography (CT) scans or magnetic resonance imaging (MRI) provide precise information about the tumor. These scans allow doctors to see the exact size and location of the adenoma and its relationship to nearby structures, such as the facial nerve, which is an important consideration for treatment planning. A pleomorphic adenoma on a CT scan often appears as a well-defined, globular mass.
The definitive diagnosis is confirmed with a tissue sample from a fine-needle aspiration (FNA). In this procedure, a thin needle is inserted into the mass to withdraw cells for a pathologist to examine. This examination identifies the characteristic mixed cell types of a pleomorphic adenoma and determines if the tumor is benign. FNA has a high rate of accuracy for determining if a tumor is malignant.
Treatment Approaches
The standard treatment for a pleomorphic adenoma is complete surgical removal. The goal is to excise the entire tumor mass to prevent it from growing back. Surgeons remove the adenoma with a margin of healthy surrounding tissue, as these tumors can have microscopic extensions that can lead to recurrence if left behind.
The surgical procedure depends on the tumor’s location and size. For tumors in the parotid gland, a parotidectomy is the most common surgery. Because the facial nerve runs directly through the parotid gland, surgeons carefully identify and preserve this nerve to prevent postoperative facial weakness. For smaller tumors, a superficial parotidectomy may be sufficient.
If the tumor is in the submandibular gland, the entire gland is removed. For adenomas in the minor salivary glands, such as on the palate, the tumor is excised with surrounding normal tissue. While surgery is the primary treatment, radiation therapy may be considered for tumors that cannot be safely removed.
Recurrence and Malignant Transformation
Recurrence after treatment is strongly linked to the completeness of the initial surgery. If any tumor cells, including microscopic extensions from the main mass, are left behind, the tumor can regrow over time. The risk of recurrence after a complete excision is low, estimated to be between 1-5%.
Pleomorphic adenomas carry a small risk of transforming into a cancerous tumor, a condition known as carcinoma ex pleomorphic adenoma. This risk is directly related to the amount of time the tumor is left in place. The likelihood of malignant change increases over many years; for example, the risk is about 1.5% within the first five years but can rise to 9.5% after fifteen years. This potential for transformation is a primary reason why surgical removal is recommended. Advanced age and a large tumor size are also associated with a higher risk of malignancy.