Follicular nodular disease of the thyroid gland

by Jason Wasserman MD PhD FRCPC
November 29, 2024

Follicular nodular disease is a benign (noncancerous) condition in which the thyroid gland develops one or more nodules, which are small, rounded areas of abnormal tissue growth. These nodules form within the thyroid gland, which is located in the lower part of the neck. When multiple nodules are present, the condition is often referred to as a multinodular goiter.

What are the symptoms of follicular nodular disease?

Most people with follicular nodular disease do not experience any symptoms. However, if the nodules grow large enough, they may cause:

• A visible or palpable lump in the neck.
• Difficulty swallowing or breathing.
• Rarely, symptoms of thyroid hormone imbalance, such as weight changes, fatigue, or heart palpitations.

What causes follicular nodular disease?

The exact cause of follicular nodular disease is not always clear. However, some factors that can contribute include:

• Iodine deficiency: A lack of iodine in the diet can lead to changes in the thyroid gland, resulting in nodule formation.
• Genetic predisposition: A family history of thyroid nodules or goiter can increase the risk.
• Thyroid inflammation: Chronic conditions like Hashimoto’s thyroiditis may lead to changes in thyroid tissue.
• Hormonal changes: Growth in thyroid nodules can sometimes be influenced by hormones such as thyroid-stimulating hormone (TSH).

How is this diagnosis made?

The diagnosis of follicular nodular disease is typically made after a combination of clinical examination, imaging, and pathology:

• Physical exam: Your doctor may feel for lumps in your neck.
• Imaging: Ultrasound is the most common imaging test for thyroid nodules. It helps assess the size, number, and characteristics of the nodules.
• Fine-needle aspiration (FNA) biopsy: A small sample of cells may be removed from a nodule and examined under a microscope to rule out cancer.
• Pathology report: If part or all of the thyroid gland is surgically removed, a pathologist examines the tissue to confirm the diagnosis.

What are the microscopic features of follicular nodular disease?

Under the microscope, follicular nodular disease shows a combination of normal thyroid tissue and areas of nodular overgrowth.

Common findings include:

• Hyperplastic follicles: Enlarged groups of thyroid cells arranged in a follicular pattern.
• Colloid: A gel-like substance produced by thyroid cells, often abundant in nodules.
• Fibrosis: Areas of scar tissue may form around the nodules.
• Degenerative changes: These may include calcification (calcium deposits), hemorrhage (bleeding), or cyst formation within the nodules.

What is the risk of developing cancer in follicular nodular disease?

The majority of thyroid nodules in follicular nodular disease are benign. However, a small percentage of nodules may harbor cancer. Features that may increase suspicion include:

• Rapid growth of a nodule.
• A nodule that feels firm or fixed to surrounding tissues.
• Suspicious findings on imaging, such as irregular borders or microcalcifications.
• A history of radiation exposure to the neck.

Your doctor may recommend further testing, such as a biopsy, to assess these risks.

What is the difference between follicular nodular disease and a goiter?

Follicular nodular disease and goiter are related but not identical terms:

• Goiter refers to an enlarged thyroid gland, which can occur with or without nodules.
• Follicular nodular disease describes a thyroid gland with one or more nodules caused by an overgrowth of follicular cells.

A goiter can develop in the context of follicular nodular disease, especially when the thyroid is significantly enlarged.

What does it mean if a dominant adenomatoid nodule was found?

A dominant adenomatoid nodule is the largest nodule in the thyroid and may require special attention. While most dominant nodules are benign, their size and appearance may prompt further evaluation to rule out cancer. By examining the nodule under the microscope, your pathologist can confirm its benign nature.

What are degenerative changes?

Degenerative changes refer to alterations within a nodule that occur over time.

These may include:

• Calcification: Deposits of calcium within the nodule.
• Cyst formation: Areas filled with fluid instead of solid tissue.
• Hemorrhage: Bleeding into the nodule, which can cause sudden swelling or pain.
• Fibrosis: Scar-like tissue forming within the nodule.

These changes are expected in long-standing nodules and do not indicate cancer.