Enlarged and hypercellular parathyroid gland

What does enlarged and hypercellular parathyroid gland mean?

Enlarged and hypercellular parathyroid gland is a term pathologists use to describe a non-cancerous growth made up of cells normally found in the parathyroid gland. The growth can involve one or more of the parathyroid glands. Unlike the normal parathyroid glands, an enlarged and hypercellular parathyroid gland may be large enough to be felt or seen in the front of the neck.

The parathyroid glands

The parathyroid glands are part of the endocrine system which means they make hormones that travel around the body through the bloodstream. Most people have four small parathyroid glands that are normally found in the front of the neck close to the much larger thyroid gland.

The parathyroid glands are made up of a combination of specialized cells called chief cells, oxyphil cells, and clear cells. These cells make parathyroid hormone (PTH) which is then released into the bloodstream. Parathyroid hormone is important because it helps control the amount of calcium in your blood. Calcium is needed to maintain strong bones and to help your nervous system, muscles, and digestive system function normally.

Hyperparathyroidism

An enlarged and hypercellular parathyroid gland often makes extra parathyroid hormone which is then released into the blood. Doctors call this hyperparathyroidism. This leads to increased levels of calcium in the blood.  Doctors call this hypercalcemia.

Symptoms of hypercalcemia include involuntary shaking (tremor), nausea, vomiting, abdominal pain, and confusion. Patients with prolonged hypercalcemia are also more likely to suffer from broken bones and kidney stones.

What causes a parathyroid gland to become enlarged and hypercellular?

The cause of an enlarged and hypercellular parathyroid gland depends on the number of glands involved and the results of other laboratory tests performed. If only a single gland is involved and your parathyroid hormone levels return to normal after the gland is removed, the growth may represent a parathyroid adenoma.

A parathyroid adenoma is a non-cancerous type of tumour and the most common cause of hyperparathyroidism. Parathyroid adenomas are often sporadic which means doctors do not know what causes them. However, some genetic syndromes such as multiple endocrine neoplasia (MEN) and familial isolated hyperparathyroidism (FIHP), greatly increase a person’s risk for developing these tumours.

If more than one parathyroid gland is involved, the condition is described as parathyroid hyperplasia. Approximately 20% of the people who develop parathyroid hyperplasia have the genetic syndrome multiple endocrine neoplasia (MEN). People with chronic kidney disease are also more likely to develop parathyroid hyperplasia. In this situation, the parathyroid glands may return to normal after treatment improves kidney function. A single enlarged and hypercellular parathyroid gland that remains after treatment is described as tertiary hyperparathyroidism.

How do pathologists make this diagnosis?

Increased levels of parathyroid hormone or calcium in your blood are often the first signs of an enlarged and hypercellular parathyroid gland. Your doctor may also suspect the diagnosis if you have a lump in the front of your neck or symptoms related to increased blood calcium (see above).

enlarged hypercellular parathyroid gland cells

If the growth is removed it will be sent to a pathologist who examines it under the microscope. The diagnosis can usually be made by examining the tissue sample stained with a combination of dyes called hematoxylin and eosin. However, some pathologists may perform an additional test called immunohistochemistry to confirm the diagnosis. The tissue sample usually shows a combination of cells normally found in the parathyroid gland.

by Archan Kakadekar MD and Jason K Wasserman MD PhD FRCPC (updated July 9, 2021)
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