Oncocytoma (salivary gland)

What is an oncocytoma of the salivary gland?

An oncocytoma is a non-cancerous tumour in the salivary glands. It is not capable of transforming into cancer over time. Most oncocytomas develop in the parotid gland, but they can be found in any of the salivary glands. Most oncocytomas are slowly growing and usually painless. Pathologists use the word oncocytosis to describe multiple oncocytomas in the same salivary gland.

The salivary glands

When we chew food our body releases fluid into the mouth called saliva. Saliva is important because it contains chemicals that help with digestion. Saliva is produced by organs called salivary glands which are located throughout the head and neck.

Most people have three major salivary glands and numerous minor salivary glands. The major salivary glands are called the parotid gland, submandibular gland, and sublingual gland. The minor salivary glands are very small and there are so many of them that they are not given their own names. Most of the minor salivary glands are found inside the mouth.

The parotid gland is the largest salivary gland and it can be found on the side of the face just in front of the ear. The submandibular gland can be found just below the lower jaw near the top of the neck. The sublingual gland is the smallest of the major glands and it can be found below the tongue.

The salivary glands are made up of small groups of cells called glands which are connected to the inside of the mouth by long thin channels called ducts. The glands make the chemicals in the saliva which travels down the ducts into the mouth.

How do pathologists make the diagnosis of oncocytoma?

The diagnosis is usually made after a small sample of tissue is removed in a procedure called a biopsy or a fine needle aspiration. The diagnosis can also be made after the entire tumour is removed in a procedure called a resection. The tissue is then sent to a pathologist who examines it under a microscope.

Under the microscope, oncocytomas are made up entirely of large pink cells. Pathologists describe these cells as oncocytic or oncocytes. The cells connect to form two rows, nests, or sheets. The nucleus of the cell is typically round and a large clump of genetic material called nucleoli are usually seen in the centre of the nucleus.

oncocytoma salivary gland

Some oncocytomas will have large spaces on the inside of the tumour. Pathologists describe these spaces as cysts. The cysts may be filled with fluid or tumour cells.

Most patients with an oncocytoma will be offered surgery to remove it. The tumour will then be sent to a pathologist who will prepare another pathology report which may include the size of the tumour removed.

What to look for in your report after the tumour has been removed

Tumour size

This is the size of the tumour measured in centimetres (cm). The tumour is usually measured in three dimensions but only the largest dimension is described in your report. For example, if the tumour measures 4.0 cm by 2.0 cm by 1.5 cm, your report will describe the tumour as being 4.0 cm.


A margin is any tissue that was cut by the surgeon in order to remove the tumour from your body. The types of margins described in your report will depend on the organ involved and the type of surgery performed.

A negative margin means that no tumour cells were seen at any of the cut edges of tissue. A margin is called positive when there are tumour cells at the very edge of the cut tissue. A positive margin is associated with a higher risk that the tumour will recur in the same site after treatment.

Margins will only be described in your report after the entire tumour has been removed. However, many pathologists will not describe margins for oncocytoma in the pathology report if they are negative.


by Jason Wasserman MD PhD FRCPC (updated August 29, 2021)
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