by Adnan Karavelic MD FRCPC
March 6, 2023
A benign follicular thyroid nodule is a very common type of non-cancerous growth in the thyroid gland. It is called a nodule because it has a round shape and stands out from the surrounding glandular tissue. The nodule is made up of follicular cells that are normally found in the thyroid gland.
Most benign follicular thyroid nodules are associated with a non-cancerous condition called nodular thyroid hyperplasia (also known as nodular follicular disease). Diffuse papillary hyperplasia (Graves disease) can also result in the development of multiple benign follicular nodules.
Patients with a benign follicular thyroid nodule typically have an enlarged thyroid gland. The enlarged thyroid can often be seen or felt on the front of the neck. Very large nodules or the presence of multiple nodules can lead to difficulty breathing, especially when lying down.
Most benign follicular nodules in the thyroid gland will not change into cancer over time, even if the nodule continues to grow. However, the development of a new nodule or growth within a previously identified nodule should be investigated with a repeat fine needle aspiration biopsy (FNAB).
Most patients with a diagnosis of benign follicular thyroid nodule will not need any additional treatment. However, surgery to remove part or all of the thyroid gland may be required if the enlarged gland starts to put pressure on surrounding tissues. Talk to your doctor about the next steps in your care.
This diagnosis is usually made after a procedure called a fine needle aspiration biopsy (FNAB) is performed on a lump or nodule in the thyroid gland. This tissue is sent to a pathologist who examines it under a microscope.
When examined under the microscope, the tissue sample typically shows follicular cells arranged in solid, flat groups called sheets. The follicular cells may also form small, round structures, called microfollicles, but this pattern tends to involve only a small amount of the tissue sample. A variable amount of colloid is typically present in the background. The follicular cells may be described as having small, round to oval nuclei, uniformly granular chromatin, smooth nuclear membranes, and a moderate amount of cytoplasm. Some of the follicular cells will be larger and bright pink. Pathologists call these Hurthle cells.
In addition, specialized immune cells such as macrophages and lymphocytes may also be seen in the tissue sample. These cells are typically seen in small groups or scattered throughout the background.