Conditions: Parotid Tumors

What and where is the parotid gland?

The parotid glands are the largest of the salivary glands. You have two of them, one on each side of the face, sitting just in front of and below each ear and wrapping around the back of the jaw. They make saliva, which drains into the mouth through a small duct that opens on the inside of the cheek, near the upper back teeth.

Two things about the parotid's anatomy matter a great deal when a lump appears in it:

• The facial nerve runs directly through it. This is the nerve that moves the muscles of the face — your smile, your blink, your forehead. It passes right through the middle of the parotid, dividing the gland into a larger superficial lobe (nearer the skin) and a smaller deep lobe. Whether a lump affects this nerve is one of the most important clues to its nature.
• The parotid contains lymph nodes inside it. Unlike the other salivary glands, the parotid has lymph nodes embedded within the gland itself. These nodes drain the scalp, forehead, eyelids, ear, and face, which is why cancers of the facial skin can later show up as a lump in the parotid.

How parotid lumps usually come to attention

Most parotid lumps are first noticed as a painless swelling or a firm bump in front of or below the ear, or near the angle of the jaw. Many are discovered by chance — while shaving, washing, or during a routine exam.

The single most important fact is reassuring: the great majority of parotid tumors are benign (not cancer). Across large studies, roughly three-quarters to nearly nine-tenths of parotid tumors are benign, and only about 12–25% are malignant. A benign tumor is not harmless to ignore, but it behaves very differently from a cancer.

Doctors pay close attention to certain features because they help separate a likely-benign lump from one that needs more concern. A lump that is soft or rubbery, moves easily under the skin, grows slowly, causes no pain, and leaves the face working normally is reassuring. The warning signs are listed later on this page.

Benign (non-cancerous) parotid tumors

Benign tumors do not spread to other parts of the body. They can, however, grow over time, and a few carry a small long-term risk of turning into cancer, which is why they are usually taken seriously even though they are not malignant.

Pleomorphic adenoma is the most common parotid tumor of all. It is sometimes called a "mixed tumor" because it is made of several tissue types. It typically appears in middle age (40s–50s), slightly more often in women, as a slow-growing, painless, firm, movable lump — usually in the superficial lobe. It is benign, but if left in place for many years it carries a small risk (a few percent) of eventually turning into a cancer, and it has a tendency to come back if not completely removed.

Warthin tumor is the second most common benign parotid tumor, and in some recent studies it is now the most common. It typically affects older adults (60s–70s) and is strongly linked to cigarette smoking — the large majority of people with this tumor are current or former smokers. It appears most often in the "tail" (lower part) of the gland, and is notable for sometimes occurring on both sides or in more than one spot. It almost never turns into cancer.

Basal cell adenoma and oncocytoma are much less common benign tumors. They usually appear in older adults as a solitary, slow-growing, painless lump and can look similar to the tumors above on scans.

Malignant (cancerous) primary parotid tumors

These are cancers that begin in the parotid gland itself. They are far less common than benign tumors, and they vary enormously — from slow-growing, highly curable cancers to aggressive ones. The main types are:

Mucoepidermoid carcinoma is the most common parotid cancer. Its behavior depends heavily on its "grade." Low-grade tumors are often slow-growing and can look and act much like a benign lump, while high-grade tumors are aggressive and may cause pain, fix to surrounding tissue, affect the facial nerve, or spread to lymph nodes.

Adenoid cystic carcinoma is a distinctive cancer known for a slow but relentless course. Pain is a common early feature, because this tumor has a strong tendency to grow along nerves (called perineural invasion). It can recur or spread to distant sites such as the lungs many years after it is first found, so patients need long-term follow-up.

Acinic cell carcinoma is usually a low-grade cancer with a generally favorable outlook. It tends to appear as a slowly growing, painless lump and is the parotid cancer most likely to occur on both sides. A minority can become more aggressive over time.

Salivary duct carcinoma is an aggressive, high-grade cancer that occurs most often in older men. It tends to grow quickly and is the parotid cancer most likely to cause facial nerve weakness at the time of diagnosis, and it often involves nearby lymph nodes.

Carcinoma ex pleomorphic adenoma is a cancer that arises out of a pre-existing benign pleomorphic adenoma. The classic story is a lump that has been present and stable for years or decades and then suddenly starts growing, becomes painful, or causes facial weakness. This change in a long-standing lump is an important warning sign.

Warning signs that a parotid lump may be cancer

No single feature is proof, and some cancers deliberately masquerade as benign lumps — in fact only a minority of parotid cancers show obvious warning signs when first found. Still, the following features raise concern and should prompt prompt evaluation:

• Pain or tenderness in the lump
• Weakness, drooping, or twitching of the face on the same side, or numbness of the face (this points to involvement of the facial or other nerves and is an especially important sign)
• The lump feeling hard and fixed — stuck to the skin or to deeper tissues rather than moving freely
• Rapid growth, or a long-standing lump that suddenly changes
• A new lump in the neck (an enlarged lymph node)
• Ulceration or breakdown of the overlying skin

Cancers that spread to the parotid from elsewhere (metastatic tumors)

Because the parotid contains lymph nodes that drain the face and scalp, it is the salivary gland most likely to be the site of a cancer that started somewhere else. In many parts of the world — especially sunny regions — these "secondary" cancers are actually more common in the parotid than cancers that begin in the gland.

• Skin cancers of the head and scalp are by far the most frequent source. Cutaneous squamous cell carcinoma is the most common, followed by melanoma; together these account for roughly 80% of cancers that spread to the parotid. High-risk skin-cancer locations include the ear, temple, cheek, forehead, and scalp. This is one reason a history of facial skin cancer is important information. Merkel cell carcinoma, another skin cancer, can also spread here.
• Other head and neck cancers, such as those of the throat or nasopharynx, occasionally spread to parotid lymph nodes.
• Cancers from below the collarbone reach the parotid much less often, through the bloodstream. The most frequently reported sources are lung, kidney, and breast cancers.

Lymphoma of the parotid

Lymphoma is a cancer of the immune system's lymphocytes (a type of white blood cell). Because the parotid contains lymph node and immune tissue, lymphoma can arise here. Most parotid lymphomas are non-Hodgkin B-cell lymphomas, and the most common type is a generally slow-growing (indolent) form called MALT lymphoma (marginal zone lymphoma). More aggressive types, such as diffuse large B-cell lymphoma, occur less often.

A key point is the strong link with Sjögren syndrome, an autoimmune disease that causes dry eyes and dry mouth and chronic inflammation of the salivary glands. People with Sjögren syndrome have a substantially higher lifetime risk of developing lymphoma — most often in the salivary glands — which is why persistent, firm, one-sided parotid swelling in someone with Sjögren syndrome is watched carefully. In autoimmune salivary swelling, a lump that becomes hard, fixed, one-sided, and persistent (rather than the usual soft swelling that comes and goes on both sides) is the feature that raises concern for lymphoma.

Conditions that can mimic a parotid tumor

Many non-cancerous conditions cause parotid swelling and can be mistaken for a tumor. Recognizing these can prevent a great deal of worry, though they often still need testing to confirm. Common mimics include:

• Salivary gland infection or inflammation (sialadenitis). A bacterial infection causes sudden, painful, red, warm swelling, sometimes with fever and pus. Viral infections — most classically mumps — tend to cause swelling on both sides. Repeated bouts can leave the gland firm and lumpy, resembling a tumor.
• Salivary stones (sialolithiasis). A stone blocking the duct causes swelling and pain that flares up around meals, when saliva is stimulated. Stones are more common in the gland under the jaw but do occur in the parotid.
• Sialadenosis. Painless, soft, symmetric enlargement of both parotids, linked to conditions such as diabetes, alcohol use, bulimia or anorexia, and malnutrition.
• Salivary cysts. Fluid-filled sacs that can feel like a solid lump and sometimes resemble a cystic tumor on scans.
• Sjögren syndrome. Beyond its lymphoma link above, the autoimmune inflammation itself causes recurring parotid swelling together with dry eyes and dry mouth.
• IgG4-related disease. An immune condition that can cause firm, painless, often two-sided swelling of the salivary glands, mimicking a tumor.
• Sarcoidosis. An inflammatory disease that can cause painless parotid swelling, occasionally along with eye inflammation, fever, and facial weakness (a combination known as Heerfordt syndrome).
• HIV-associated salivary cysts. Multiple cysts in both parotid glands can be an early sign of HIV infection.
• First branchial cleft cyst. A congenital (present-from-birth) cyst near or within the parotid that may not cause trouble until it becomes infected.
• Other rare mimics, including certain vascular growths, amyloid deposits, and air trapped in the duct (pneumoparotitis, seen in wind-instrument players).

How a parotid lump is evaluated

The goal of the workup is to answer two questions: what is this, and is it benign or malignant. (Treatment is covered on the Parotid Tumors treatment page.)

• History and physical examination. The doctor asks how long the lump has been present, whether it is painful or growing, and whether there is any facial weakness, and checks the movement of the face, the texture and mobility of the lump, and the neck for enlarged nodes.
• Imaging. Ultrasound is usually the first test — it is quick, painless, uses no radiation, and can often be used to guide a needle biopsy. CT or MRI scans are used to see deeper parts of the gland, assess the lump's extent, and check for nerve or bone involvement; MRI is especially good for soft tissue and nerve detail.
• Needle biopsy. A fine-needle aspiration — drawing a small sample of cells through a thin needle — is the standard way to sample a parotid lump and is often done with ultrasound guidance. It is accurate in most cases, though it cannot always give a definitive answer, and sometimes a slightly larger core needle biopsy is used. An open (surgical) biopsy that cuts into the lump is generally avoided, because it can risk spreading tumor cells.

When to seek medical attention

Any new lump in front of or below the ear or near the jaw deserves evaluation, even if it is painless. Seek care promptly if a parotid lump is painful, growing quickly, hard and fixed in place, or associated with weakness or drooping of the face, numbness, skin changes over the lump, or a new lump in the neck.

Questions you may want to ask your doctor

• Does my lump have any of the warning features that suggest it needs urgent attention?
• What imaging and biopsy tests do I need, and what will they tell us?
• Is this likely a tumor starting in the gland, something that spread from elsewhere, or a mimic such as an infection or inflammation?
• Do I need any evaluation of my facial nerve function?
• If a biopsy is not definitive, what are the next steps?