Oncocytic

The term oncocytic is used by pathologists to describe cells that appear bright pink under the microscope when stained with a routine stain called hematoxylin and eosin (H&E). These cells look pink because their cytoplasm (the body of the cell) is packed with mitochondria, which are small structures that produce energy for the cell. The large number of mitochondria causes the cytoplasm to stain strongly with eosin, a pink dye.

Oncocytic cells often appear larger and more granular than other nearby cells. They can be found in many tissues in the body and may be seen in both normal conditions and in tumours.

Where are oncocytic cells normally found?

Oncocytic cells can occur in a variety of tissues, including the thyroid, salivary glands, kidneys, parathyroid glands, and adrenal glands. In some organs, oncocytic cells are part of normal aging or long-standing tissue stress.

Cells that were not originally oncocytic can become oncocytic over time, a process called oncocytic metaplasia. This change is usually not harmful, but it can be seen in both benign and cancerous conditions.

In the thyroid gland, oncocytic cells are often called Hürthle cells. These are follicular thyroid cells that have developed oncocytic features, and the terms Hürthle cell metaplasia or oncocytic metaplasia are often used interchangeably.

What types of tumours are made of oncocytic cells?

Tumours made up of oncocytic cells can be either benign (non-cancerous) or malignant (cancerous). These tumours are often named based on their appearance and where they arise in the body.

Oncocytoma

An oncocytoma is a benign tumour made entirely of oncocytic cells. These tumours do not invade nearby tissues or spread to other parts of the body. Oncocytomas most commonly arise in the kidneys and salivary glands, but they can also occur in the thyroid, adrenal glands, and other areas. Although oncocytomas are non-cancerous, they may still be removed if they cause symptoms or are difficult to distinguish from cancer on imaging studies.

Oncocytic carcinoma

An oncocytic carcinoma is a malignant tumour made up of oncocytic cells. These tumours can grow into nearby tissues and may spread (metastasize) to other parts of the body. Most oncocytic carcinomas develop in the head and neck, especially in the salivary glands such as the parotid or submandibular glands.

Hürthle cell carcinoma

In the thyroid gland, a cancer made up of oncocytic cells is called Hürthle cell carcinoma. This is a specific type of follicular thyroid carcinoma in which the tumour cells show oncocytic features. Hürthle cell carcinoma can invade nearby blood vessels or tissues and may spread to other parts of the body, although it often grows more slowly than other types of thyroid cancer.

What does the presence of oncocytic cells mean?

The presence of oncocytic cells in a pathology report is a descriptive finding, not a diagnosis by itself. The meaning of the finding depends on the context:

• In normal tissue, oncocytic cells may be part of age-related changes or long-standing inflammation.

• In benign conditions, oncocytic metaplasia may be seen without any concern for cancer.

• In tumours, the presence of oncocytic cells helps pathologists classify the tumour and decide whether it is benign or malignant.

Your doctor will use the full pathology report, including any additional features such as tumour size, invasion, or spread, to determine whether the oncocytic cells are part of a cancer and what treatment may be needed.

Questions to ask your doctor

• What does the term “oncocytic” mean in my report?

• Are the oncocytic cells part of a benign or malignant tumour?

• What is the name of the tumour diagnosed?

• Will I need additional tests or treatment?

• Should the tumour be removed or monitored?