Adenomatoid nodule of the thyroid gland

by Jason Wasserman MD PhD FRCPC
May 16, 2024

An adenomatoid nodule in the thyroid gland refers to a benign (noncancerous) growth, often classified under the broader category of nodular thyroid disease. These nodules are termed “adenomatoid” because they resemble benign tumors known as follicular adenomas; however, they are distinct in that they lack a complete fibrous capsule and often merge with the surrounding normal thyroid tissue. These growths are most common in younger women, although they can be seen in adults of all ages.

What causes an adenomatoid nodule?

The exact cause of adenomatoid nodules is not fully understood, but they are thought to result from various factors, including hormonal imbalances, iodine deficiency, and genetic predispositions. They are often seen as a response to the thyroid gland’s attempt to produce sufficient hormones, leading to localized overgrowths.

What are the symptoms of an adenomatoid nodule?

Adenomatoid nodules are typically asymptomatic, especially when they are small. Large nodules, however, may cause symptoms due to their size or location, such as pressure effects on the trachea or esophagus, leading to difficulty swallowing, breathing problems, or neck discomfort. Thyroid function can be normal, overactive, or underactive, depending on the nature of the nodular disease. Larger nodules may appear as a lump in the front of the neck.

Association with nodular follicular disease

Adenomatoid nodules are a key component of nodular follicular disease of the thyroid gland, which encompasses a spectrum of nodular conditions, including solitary thyroid nodules and multinodular goiter. Nodular follicular disease typically involves multiple adenomatoid nodules, varying widely in size and activity.

Microscopic appearance

Under the microscope, adenomatoid nodules appear round and well-circumscribed. A fibrous capsule partially surrounds some. The nodule is characterized by a proliferation of follicular cells that tend to vary in size, with most being macrofollicles. These larger follicles are filled with colloid, a gel-like substance produced by the follicular cells. This contributes to the darker, more homogenous appearance than the normal thyroid tissue surrounding it.

About this article

Doctors wrote this article to help you read and understand your pathology report. Contact us if you have any questions about this article or your pathology report. Read this article for a more general introduction to the parts of a typical pathology report.

Other helpful resources

Atlas of Pathology