Warthin Tumor: Understanding Your Pathology Report

by Jason Wasserman MD PhD FRCPC
May 8, 2026

Warthin tumor is a noncancerous tumor that almost always starts in the parotid gland — the largest salivary gland, which sits in front of and below each ear. It is the second most common salivary gland tumor, after pleomorphic adenoma. Warthin tumor is benign — it does not spread to other parts of the body or invade surrounding tissues. It often grows very slowly or not at all over many years, and a growing number of patients with small or symptom-free Warthin tumors are simply followed with imaging rather than having surgery. You may see Warthin tumor referred to in older reports by other names, including papillary cystadenoma lymphomatosum or adenolymphoma, but these terms are no longer used.

This article will help you understand the findings in your pathology report — what each term means and why it matters for your care.

What causes Warthin tumor?

The cause of Warthin tumor is not fully understood, but the strongest known risk factor by far is cigarette smoking. People who smoke are 7 to 8 times more likely to develop a Warthin tumor than people who do not smoke. Smokers are also more likely to develop multiple tumors at the same time and to have tumors on both sides of the face. Other possible risk factors include:

Radiation exposure to the head or neck — A weak risk factor that has been described in atomic bomb survivors and in people who received radiation therapy in childhood.
Autoimmune conditions — Some studies suggest a link with autoimmune diseases such as Hashimoto thyroiditis, but the connection is not fully established.
Viral and immune-related factors — Some research has suggested a possible link with Epstein-Barr virus and other immune-related processes, but these connections are still being studied.

Most Warthin tumors do not have a single specific DNA change that drives their growth. Warthin tumor is thought to arise from small clusters of salivary gland tissue that became trapped inside lymph nodes near the parotid gland during embryonic development. This unusual origin is why Warthin tumor often has a heavy lymphoid (immune cell) background under the microscope and why it can sometimes be found inside a nearby lymph node.

Where does Warthin tumor start?

More than 95% of Warthin tumors start in the parotid gland — most often in the lower part of the gland near the angle of the jaw, an area pathologists call the tail of the parotid. The tumor occurs much less often in other salivary glands. A few features set Warthin tumor apart from most other salivary gland tumors:

Bilateral tumors — About 10–15% of patients have a Warthin tumor on each side of the face, either at the same time or developing one after the other.
Multifocal tumors — About 10–20% of patients have more than one Warthin tumor in the same parotid gland.
Tumor in nearby lymph nodes — Because of how Warthin tumor forms, it can sometimes be found inside a lymph node next to the parotid gland. This is not a sign of spread or cancer.

Warthin tumor most often affects older adults, with an average age at diagnosis of about 62 years. It is rare in children. Historically, Warthin tumor was much more common in men than in women, with male-to-female ratios as high as 10 to 1 in older studies. As smoking rates among women rose during the 20th century, this gap narrowed considerably, and the difference between men and women is now small. Warthin tumor is also less common in Black African populations than in other groups.

What are the symptoms of Warthin tumor?

Most Warthin tumors grow slowly or not at all over many years and produce few symptoms:

Painless lump — A soft or rubbery, slow-growing, painless lump near the angle of the jaw or below the ear is the most common finding by far.
Sensation of fullness — Some patients describe a feeling of pressure or fullness in the area before they can feel a definite lump.
Discomfort with very large tumors — Larger tumors can cause mild discomfort or a noticeable bulge along the jawline.
Pain or facial weakness — Uncommon. When new pain or facial weakness develops, it is most often caused by a particular variant of Warthin tumor called metaplastic or infarcted Warthin tumor — a tumor in which the cells have been damaged (often after a needle biopsy) and the area becomes inflamed. New pain or facial weakness is also a reason to consider whether something more serious is going on, and your doctor will usually order additional tests.
Lumps on both sides of the face — About 10–15% of patients notice a lump on each side, since Warthin tumor can occur on both sides.

How is the diagnosis made?

The diagnosis is made after a tissue sample is examined under the microscope by a pathologist. Most patients first have an imaging test — usually an ultrasound, CT scan, or MRI — that shows a well-defined mass with cystic (fluid-filled) areas in the parotid gland. Multiple tumors on imaging are a clue that the diagnosis may be Warthin tumor. A fine needle aspiration biopsy (FNAB) is often done first to take a small sample of cells through a thin needle. The combination of granular oncocytic cells and lymphocytes (with cyst fluid in the background) on FNAB is highly suggestive of Warthin tumor. A core needle biopsy or surgical removal of the tumor may also be done if the diagnosis is unclear after FNAB.

Under the microscope, Warthin tumor has a very distinctive appearance, made up of two parts arranged together:

Epithelial cells — The cells form a two-layered (bilayered) lining around fluid-filled cystic spaces and finger-like (papillary) projections. The inner layer is made up of tall column-shaped cells, while the outer layer is made up of smaller cube-shaped (cuboidal) cells. Both layers are oncocytic — meaning the cells have a granular pink appearance under the microscope. The granular look comes from large numbers of mitochondria (the energy-producing structures inside cells) packed into the cytoplasm.
Lymphoid stroma — The supporting tissue around and beneath the epithelial cells looks very similar to the inside of a normal lymph node. It contains many lymphocytes (immune cells) and often shows reactive structures called germinal centers, which are small round clusters of immune cells.

In some cases, Warthin tumors show metaplastic changes — areas where the typical oncocytic cells have been replaced by squamous (skin-like) or mucinous (mucus-producing) cells. These changes are most often seen in tumors that have been previously biopsied or that have areas of damage and inflammation (called infarction). Although metaplastic changes can look concerning under the microscope, they are not a sign of cancer.

The most important condition that Warthin tumor — particularly the metaplastic variant — must be told apart from is mucoepidermoid carcinoma, a salivary gland cancer that also contains squamous and mucinous cells. In difficult cases, the pathologist may order a molecular test to look for a fusion involving the MAML2 gene. This fusion is found in most mucoepidermoid carcinomas but is not typically seen in Warthin tumor. The most useful tests for finding this fusion are next-generation sequencing (NGS) and fluorescence in situ hybridization (FISH). For most Warthin tumors, however, no molecular testing is needed because the microscopic appearance is enough to make the diagnosis.

Surgical margins

A margin is the edge of the tissue that the surgeon cuts when removing the tumor. The pathologist examines these edges under the microscope to see whether any tumor cells reach the cut surface.

Negative margin — No tumor cells are seen at the cut edge. This suggests the tumor was completely removed.
Positive margin — Tumor cells are seen at the cut edge of the tissue. In a benign tumor like Warthin tumor, a positive margin does not usually mean further treatment is needed, but the surgeon may recommend closer follow-up to watch for the tumor coming back.

Margin status is generally less critical for Warthin tumor than for cancerous salivary gland tumors because Warthin tumor is benign and does not invade surrounding tissues. However, when a Warthin tumor does come back after surgery, it is often because more than one tumor was present originally and not all were found, rather than because of a positive margin.

Can a Warthin tumor turn into cancer?

Almost never. Malignant transformation of a Warthin tumor — either of the epithelial component or of the lymphoid component — is extraordinarily rare and has only been described in a handful of case reports in the medical literature. In practical terms, a Warthin tumor diagnosis means there is essentially no chance the tumor will turn into cancer. This is one of the reasons many patients with small, asymptomatic Warthin tumors can be safely followed without surgery.

What is the prognosis?

The outlook for Warthin tumor is excellent. It is benign, does not spread, and almost never turns into cancer. Once a Warthin tumor has been removed, true recurrence at the same site is uncommon. When new tumors appear after surgery, they are usually new Warthin tumors arising at a different spot in the parotid gland or on the opposite side, rather than the original tumor coming back. This reflects the multifocal nature of the disease, particularly in smokers. Long-term survival is the same as for the general population, and Warthin tumor itself does not shorten life.

What happens after the diagnosis?

Treatment of Warthin tumor is led by a head and neck surgeon. Both surgical removal and active surveillance are reasonable options for many patients, and the choice depends on the tumor size, whether it is causing symptoms, the patient’s overall health, and personal preference.

Surgical removal — The traditional treatment. Most parotid Warthin tumors can be removed with a partial or superficial parotidectomy that takes out the tumor along with a small rim of surrounding gland tissue. The facial nerve, which runs through the parotid gland, is preserved whenever possible. Surgery is typically recommended when the tumor is causing symptoms, is growing, is uncertain on imaging or biopsy, or is cosmetically bothersome.
Active surveillance — An increasingly common option for older patients with small, symptom-free Warthin tumors and for patients with multiple tumors that would be difficult to remove all at once. Because Warthin tumor is benign, grows very slowly, and almost never turns into cancer, simply following the tumor with periodic ultrasound or other imaging is a safe alternative to surgery in many situations. Active surveillance avoids the risks of parotid surgery, which include facial nerve injury, dryness of the mouth, and a small risk of an unusual sweating reaction called Frey syndrome.
Repeat surgery — Rarely needed. May be considered when a new tumor develops at a different site, when an incompletely removed tumor begins to grow again, or when the original diagnosis is uncertain.
Long-term follow-up — For both surgical and surveillance approaches, periodic clinical examination is reasonable to watch for new tumors on either side. The risk of new tumors is highest in smokers, so quitting smoking can lower the chance of additional Warthin tumors developing.

Radiation therapy and chemotherapy are not used for Warthin tumor.

Questions to ask your doctor

Where exactly was the tumor located, and how large was it?
Do I have only one Warthin tumor, or are there more than one, including on the other side?
Is surgery necessary in my case, or would active surveillance be a reasonable option?
If surgery is recommended, what type will be done, and what are the risks of facial nerve injury or other complications?
If I choose active surveillance, what is the schedule for follow-up imaging?
Was the tumor completely removed? What were the surgical margins?
Will the tumor come back, either at the same site or somewhere else?
Could the tumor turn into cancer, and what would that look like if it happened?
Will quitting smoking lower my chance of developing more Warthin tumors?
Will I have any lasting facial weakness, numbness, or dry mouth from the surgery?