Pleomorphic adenoma is the most common benign tumor of the salivary glands, particularly affecting the parotid gland. Although non-cancerous in most cases, this tumor requires careful evaluation and timely management to prevent complications. Understanding its nature, growth behavior, and treatment options is essential for patients and caregivers alike.

What Is Pleomorphic Adenoma?

Pleomorphic adenoma, also known as a benign mixed tumor, is a slow-growing, non-cancerous tumor that most frequently arises in the parotid gland. The parotid gland is the largest of the salivary glands and is located in front of the ear, extending down to the angle of the jaw.

The gland develops early during embryonic growth, at the same time as lymph nodes and the facial nerve. As a result, in a fully developed individual, the parotid gland is closely associated with the facial nerve — the main nerve responsible for facial movements — and nearby lymph nodes. This close anatomical relationship makes surgical treatment delicate and highly specialized.

Parotid Tumors and Their Types

Parotid tumors are abnormal growths (neoplasms) of the parotid gland. Approximately 85% of parotid tumors are benign (non-cancerous), while about 15% are malignant (cancerous).

Among all parotid tumors, pleomorphic adenoma is the most common type. Other benign tumors include:

• Warthin’s tumor (papillary cystadenoma lymphomatosum)
• Oncocytomas
• Monomorphic adenomas
• Hemangiomas (especially common in children)
• Benign lymphoepithelial lesions (often associated with HIV-positive individuals)

While these tumors differ in behavior and origin, pleomorphic adenoma remains the most frequently diagnosed.

Why Is It Called “Pleomorphic”?

The term “pleomorphic” refers to the tumor’s varied cellular appearance under the microscope. It contains a mixture of epithelial (glandular) and mesenchymal (connective tissue-like) components. This mixed structure gives it its alternative name — benign mixed tumor.

Despite its complex microscopic appearance, pleomorphic adenoma typically has well-defined edges. Unlike malignant tumors, it usually does not invade surrounding tissues aggressively.

Symptoms of Pleomorphic Adenoma

Pleomorphic adenoma generally presents as:

• A painless, slow-growing lump near the ear or jaw
• A firm, mobile swelling in the parotid region
• Gradual enlargement over months or years

Because the tumor grows slowly and is often painless, many patients delay seeking medical attention. However, as the tumor increases in size, it may become more noticeable and cosmetically concerning.

Facial nerve weakness is uncommon in benign tumors like pleomorphic adenoma. If facial weakness occurs, it may raise suspicion for malignancy.

Growth Pattern and Risks

Although pleomorphic adenoma is benign, it should not be ignored. There are two major concerns:

1. Progressive Enlargement

These tumors continue to grow over time. As they enlarge, surgical removal becomes more complex, especially because of the close relationship between the tumor and the facial nerve.

2. Malignant Transformation

In approximately 5% to 15% of cases, pleomorphic adenoma can transform into a malignant tumor known as carcinoma ex-pleomorphic adenoma. This transformation usually occurs in long-standing, untreated tumors.

Early detection and surgical removal significantly reduce this risk.

Diagnosis

Diagnosis of pleomorphic adenoma typically involves:

• Clinical examination
• Imaging studies such as ultrasound, CT scan, or MRI
• Fine needle aspiration cytology (FNAC)

Imaging helps determine the size, location, and relationship of the tumor to the facial nerve. FNAC provides cellular samples to confirm whether the tumor is benign or suspicious for malignancy.

Treatment: Surgical Excision

The standard treatment for pleomorphic adenoma is surgical removal, most commonly through a procedure called parotidectomy.

What Is Parotidectomy?

Parotidectomy is the surgical removal of part or all of the parotid gland. Depending on the tumor’s location, the surgeon may perform:

• Superficial parotidectomy (removal of the outer portion)
• Total parotidectomy (removal of the entire gland)

The primary goal of surgery is complete removal of the tumor while preserving the facial nerve.

In some cases, surgeons may combine parotidectomy techniques with cosmetic approaches similar to a facelift incision to reduce visible scarring.

Recurrence and Prognosis

When properly excised, pleomorphic adenoma has an excellent prognosis. However, recurrence can occur if:

• The tumor capsule is ruptured during surgery
• The tumor is incompletely removed
• Microscopic extensions are left behind

Recurrent tumors can be more difficult to manage due to scar tissue and altered anatomy.

Overall, early and complete surgical treatment offers a high cure rate with minimal complications.

Other Benign Parotid Tumors

For comparison, Warthin’s tumor is the second most common benign parotid tumor. It does not typically transform into cancer but may occur on both sides. Hemangiomas are the most common parotid tumors in children. Benign lymphoepithelial lesions may appear in HIV-positive individuals and are treated if they cause cosmetic deformity or raise suspicion of lymphoma.

Each tumor type requires individualized evaluation, but surgical excision remains the mainstay of treatment for most benign parotid tumors.

When to Seek Medical Attention

Any persistent swelling near the ear, jaw, or parotid region should be evaluated by a specialist. Early assessment helps determine whether the mass is benign or malignant and allows for timely treatment.

Delaying care can increase the risk of tumor growth and potential malignant transformation.

Pleomorphic adenoma is a common, usually benign tumor of the parotid gland. While not cancerous in most cases, it requires proper diagnosis and surgical management to prevent complications. Early detection, careful surgical planning, and preservation of the facial nerve are critical for optimal outcomes.

For evaluation and treatment of pleomorphic adenoma and other parotid tumors, our organization provides specialized surgical care using advanced techniques focused on safety, precision, and patient-centered management.