Pleomorphic Adenoma: Symptoms, Diagnosis, and Treatment

Pleomorphic adenoma is the most common benign tumor of the salivary glands, accounting for the majority of salivary gland neoplasms overall. It typically shows up as a slow-growing, painless lump near the jaw or in the mouth, most often in the parotid gland, the large salivary gland just in front of each ear. Despite being benign, it demands attention because of its tendency to recur after incomplete removal and a small but real risk of transforming into a cancer over time.

Where It Develops and Who Gets It

About 80% of pleomorphic adenomas arise in the parotid gland, with roughly 10% appearing in the minor salivary glands scattered throughout the mouth, primarily the palate, lips, and cheeks.¹ The submandibular gland, tucked beneath the lower jaw, accounts for most of the remainder. Women are affected more often than men, making up about 60% of cases. The tumor can appear at any age, but the peak incidence falls between 40 and 60 years old.¹

The exact cause remains unknown. A history of radiation to the head and neck area is one of the few established risk factors. Some occupational exposures, including work in rubber manufacturing and asbestos-related industries, have been flagged as potential contributors, along with smoking and heavy alcohol use, though the evidence tying any single environmental factor to this tumor is not strong enough to point fingers with certainty.

What It Looks and Feels Like

The hallmark symptom is a painless, firm lump that grows slowly over months or even years. When it arises in the parotid gland, you typically notice a mass just below or in front of the ear, sometimes extending toward the angle of the jaw. The lump is usually smooth, mobile under the skin, and not tender to touch. Because it grows so gradually, many people live with it for a long time before seeking medical attention.

Pain is uncommon and, when present, can signal that the tumor is pressing on nearby nerves or, less reassuringly, that something more aggressive is happening. Facial nerve weakness, such as drooping on one side of the face, is rare with a straightforward pleomorphic adenoma and should prompt immediate evaluation, since it raises concern for a malignant process.

When the tumor develops in a minor salivary gland, the presentation is different. A pleomorphic adenoma on the palate shows up as a smooth, dome-shaped swelling on the roof of the mouth, usually on one side. It is firm, covered by normal-looking mucosa, and painless. On the lip or cheek, it feels like a small rubbery nodule just beneath the surface. These intraoral tumors are easy to dismiss as something insignificant, which is one reason they sometimes grow quite large before anyone investigates.

Why “Pleomorphic”

The name refers to the tumor’s remarkable variety under the microscope. Unlike most tumors that look relatively uniform, pleomorphic adenoma contains a mix of epithelial cells and stromal tissue that can include areas resembling cartilage, bone, or mucoid material.² The presence of a characteristic cartilage-like stroma is one of the features pathologists look for when making the diagnosis.³ This internal diversity is what gives the tumor its name, and it can occasionally make diagnosis tricky when the tissue sample shows an unusual pattern.

At the genetic level, the main events driving pleomorphic adenoma involve rearrangements of two genes, PLAG1 and HMGA2, which lead to overproduction of their respective proteins.⁴ These same genetic changes show up again in cases that transform into cancer, which has made them a focus of research into how and why that transformation occurs.⁵

How It Is Diagnosed

Diagnosis usually begins with imaging. Ultrasound is often the first step because it is quick, widely available, and gives a good initial look at a parotid mass. On ultrasound, a pleomorphic adenoma typically appears as a well-defined, solid mass that may have a lobulated shape. Compared to Warthin tumor, the other common benign parotid tumor, pleomorphic adenomas tend to show less internal blood flow and fewer cystic areas.⁶

If ultrasound identifies a solid mass, MRI is the next step. MRI provides far more detail about the tumor’s size, its relationship to the facial nerve, and whether it extends into the deep lobe of the parotid gland. On MRI, pleomorphic adenomas appear as well-defined, rounded masses that are bright on fluid-sensitive sequences and enhance uniformly with contrast.⁷ This characteristic appearance helps distinguish them from other parotid tumors, though overlap exists. Pleomorphic adenomas are more likely to occur in younger patients, affect women, and show delayed enhancement compared to Warthin tumors.⁸

A tissue sample is usually needed to confirm the diagnosis before surgery. Fine needle aspiration, where a thin needle is inserted into the mass to collect cells, is the traditional approach. It is safe and minimally invasive, but its accuracy has limits. One study of parotid tumors found moderate agreement between fine needle aspiration results and the final surgical pathology, with a sensitivity for detecting malignancy of about 69% and specificity around 90%.⁹ Core needle biopsy, which retrieves a larger tissue sample, has been shown to provide higher sensitivity and more accurate tumor subtyping without major complications.¹⁰ The choice between the two often depends on institutional preference and the clinical situation.

Surgical Treatment

Surgery is the standard treatment for pleomorphic adenoma. Simply shelling the tumor out of its bed, a technique called enucleation, was common decades ago but fell out of favor because it led to unacceptably high recurrence rates. The tumor lacks a true fibrous capsule; instead, it is surrounded by a thin pseudocapsule, and fingerlike extensions of tumor tissue frequently push through it into the surrounding gland.¹¹ Leaving those extensions behind is the main reason tumors come back.

For parotid tumors, two main surgical approaches are used today. Superficial parotidectomy removes the entire superficial lobe of the parotid gland along with the tumor, providing wide margins. Extracapsular dissection is a more conservative procedure that removes the tumor with a cuff of normal tissue while preserving as much of the gland as possible. A 2025 meta-analysis of over 2,500 patients found that recurrence rates were similar between the two approaches, but extracapsular dissection resulted in less temporary facial nerve weakness and a lower rate of Frey syndrome, a condition where the cheek sweats during eating.¹² Based on these findings, extracapsular dissection is increasingly considered the preferred option for tumors up to 3 cm in size that are mobile and located in the superficial lobe. Traditional parotidectomy remains the better choice for larger or more complex tumors.¹³

For tumors in the minor salivary glands, such as those on the palate, wide local excision is the standard. The surgeon removes the tumor along with a margin of normal tissue, including the overlying mucosa and underlying periosteum, to reduce the chance of recurrence.¹⁴

What to Expect After Surgery

Most people recover well from parotid surgery, but the operation carries specific risks worth knowing about. Numbness around the ear and lower cheek is the most common complaint and occurs because a sensory nerve called the great auricular nerve runs through the surgical field. When the nerve must be cut or is injured, you lose sensation in that area. Numbness was the most frequently reported symptom in one quality-of-life study, and its severity correlated with whether the nerve had been sacrificed.¹⁵ The encouraging news is that numbness and pain tend to improve substantially over time. A long-term follow-up study found that both symptoms were significantly reduced after 13 years compared to the early postoperative period, and overall quality of life improved as well.¹⁶

Frey syndrome, where the skin over the surgical site sweats and flushes while eating, is another recognized complication. It happens because regenerating nerve fibers from the cut parasympathetic nerves that used to stimulate saliva production instead grow into the sweat glands of the overlying skin. One study found that about 21% of patients had symptoms along with a positive diagnostic test for the condition after partial parotidectomy.¹⁷ It is more common after superficial parotidectomy than after extracapsular dissection. For most people it is a mild annoyance rather than a serious problem, and botulinum toxin injections can control it when needed.

Patient satisfaction after parotid surgery for benign disease is generally high, including satisfaction with cosmetic outcomes.¹⁵ The rate of disease-specific impairment drops from about 70% at six weeks after surgery to around 30% many years later, so the trajectory is consistently one of improvement.¹⁶

Recurrence and How to Manage It

Recurrence is the defining challenge of pleomorphic adenoma management. Unlike most benign tumors, which stay gone once removed, pleomorphic adenoma can reappear years or even decades later. The pseudocapsule and its fingerlike tumor extensions are the primary explanation. In one study, 56% of the primary tumors that later recurred had sent tumor extensions outside the pseudocapsule, and this was the only feature significantly associated with recurrence risk.¹¹ Rupture of the tumor capsule during surgery, which spills tumor cells into the wound bed, also raises the odds.

Recurrent disease is harder to treat than the original tumor. Each subsequent operation carries a greater risk of damaging the facial nerve because scar tissue from previous surgery obscures the normal anatomy. French clinical guidelines recommend MRI before any revision surgery to map the extent of disease and detect small satellite nodules that might not be palpable.¹⁸ Surgery with nerve monitoring is the recommended approach, and the surgeon aims for complete removal of all visible and microscopic disease.

Radiation therapy enters the picture mainly for recurrent tumors. After surgery for a first-time pleomorphic adenoma, radiation is almost never used. But for tumors that have recurred multiple times, or when the surgeon suspects microscopic residual disease, postoperative radiation dramatically reduces the chance of yet another recurrence. One study of 49 patients with recurrent disease found that among those treated with surgery alone, 34 experienced further recurrences, compared to just 1 recurrence among those who also received radiation.¹⁹ Other studies confirm that this combination provides excellent long-term tumor control with acceptably low rates of late complications, including a low incidence of radiation-induced second cancers.²⁰

The Risk of Turning Malignant

One of the more unsettling aspects of pleomorphic adenoma is that it can, in rare cases, transform into a malignancy called carcinoma ex pleomorphic adenoma. This is not a rapid event. It typically occurs in tumors that have been present for many years, often untreated or recurrent. Larger tumor size at presentation and older patient age are both associated with a higher likelihood of this transformation.²¹

Among patients who present with recurrent pleomorphic adenoma specifically, several factors tip the odds toward a malignant diagnosis. Being over 50, having a significant smoking history, and having a tumor larger than 2 cm on pathology were all independently associated with carcinoma ex pleomorphic adenoma in one analysis.²² The same PLAG1 and HMGA2 genetic alterations found in benign pleomorphic adenomas persist in their malignant counterparts, suggesting the cancer evolves from the pre-existing benign tumor rather than arising independently.²³

This risk of malignant change is one of the strongest arguments for not taking a “watch and wait” approach with pleomorphic adenomas, even though they are benign. Removing the tumor while it is still small and localized eliminates not only the tumor itself but also the possibility of it evolving into something far more dangerous down the line. Younger patients deserve particular attention here, since their longer life expectancy means more years during which transformation could potentially occur.¹⁸

Pleomorphic Adenoma in Children and Adolescents

Salivary gland tumors are rare in the pediatric population, but when they do occur, pleomorphic adenoma is the most common type, just as in adults. A review of 90 pediatric and adolescent cases found a median age of about 16 and a half years, with girls affected roughly 1.4 times more often than boys.²⁴ The parotid was the most commonly affected major gland, and the palate was the most common minor salivary gland site, mirroring the adult pattern.

There are some differences worth noting. The distribution of histologic subtypes in children does not perfectly match what is seen in adults, and the tumors may behave slightly differently in terms of location patterns.²⁴ Minor salivary gland tumors in children are particularly uncommon, accounting for fewer than 10% of pediatric salivary gland tumor cases.⁷ Surgical removal remains the treatment of choice regardless of age, and outcomes are generally excellent. Given the long timeline over which recurrence and malignant transformation can occur, lifelong follow-up is especially important for patients diagnosed young.

Advances in MRI Techniques

Standard MRI is already useful for evaluating salivary gland masses, but newer techniques are pushing diagnostic accuracy even higher. Diffusion-weighted imaging, which measures how freely water molecules move within tissue, can help distinguish pleomorphic adenoma from other tumor types. Pleomorphic adenomas tend to have higher water diffusion values than both Warthin tumors and malignant salivary tumors, reflecting their looser internal structure.²⁵

Dynamic contrast-enhanced MRI, which tracks how the contrast agent flows in and out of the tumor over time, adds another layer of information. One study found that a specific measurement of contrast washout achieved about 97% accuracy in identifying pleomorphic adenomas and separating them from both Warthin tumors and malignant lesions.²⁶ Another technique called intravoxel incoherent motion imaging, which separates tissue diffusion from microcirculation effects, has shown overall accuracy around 86% for distinguishing benign from malignant salivary tumors, outperforming standard diffusion-weighted imaging alone.²⁷

These techniques are not yet universally available, and many centers still rely on conventional MRI supplemented by biopsy. But they represent a meaningful shift toward being able to characterize a salivary gland mass with greater confidence before the patient ever reaches the operating room. For tumors in difficult locations, or in patients where the biopsy result was inconclusive, advanced MRI can be the piece of information that tips the decision toward surgery or reassurance.

Palatal Pleomorphic Adenomas as a Distinct Challenge

Tumors arising from the minor salivary glands of the hard palate deserve separate mention because they present unique surgical considerations. The palate is the most common location for minor salivary gland pleomorphic adenomas, and the tumor usually appears as a firm, smooth, painless swelling to one side of the midline.¹⁴ Unlike in the parotid gland, where the tumor is surrounded by glandular tissue, palatal tumors sit between the mucosa above and the bone below. They do not have a well-formed capsule here, which means the boundary between tumor and normal tissue can be indistinct.

The surgical approach for palatal tumors involves wide excision including the mucosa and the periosteum down to bone. In one reported case, a palatal pleomorphic adenoma recurred ten years after the initial surgery, which had been performed by simple enucleation. The recurrence was then treated with a more extensive excision including wide margins, and the patient remained recurrence-free at two years of follow-up.²⁸ The lesson is consistent across settings: conservative removal that leaves any tumor tissue behind invites recurrence, and wide excision from the outset saves patients from needing a second, more difficult surgery years down the road.