Benign follicular nodule is a term pathologists use to describe a group of non-cancerous conditions in the thyroid gland. This diagnosis is usually made after a procedure called a fine-needle aspiration or FNA. All the conditions in this group are made up of cells that look similar when examined under the microscope.
The following conditions can cause a benign follicular nodule:
Most of the time it is not possible for a pathologist to tell the difference between these conditions when examining tissue removed by fine-needle aspiration. For that reason, the term benign follicular nodule is used in place of a more specific diagnosis.
The thyroid is a small U-shaped gland located in the front of the neck. It is made up of two halves, called lobes, which lie along the trachea and are joined together by a narrow band of thyroid tissue, known as the isthmus.
The function of the thyroid gland is to take iodine, found in many foods, and convert it into thyroid hormone. Once made, the thyroid hormone is released into the bloodstream and transported throughout the body where they control the body’s metabolism (e.g. the conversion of oxygen and calories to energy).
Most of the cells in the thyroid gland are called follicular cells. The follicular cells connect together to form small round structures called follicles. Thyroid hormone is stored in a material called colloid which fills the center of follicles.
Patients with a benign follicular nodule typically have an enlarged thyroid gland. The enlarged thyroid can often be seen or felt on the front of the neck. A special camera called an ultrasound will be used to look inside the gland for any abnormal areas. At the same time, a procedure called a fine needle aspiration will be performed to remove a small sample of tissue. This tissue is sent to a pathologist who examines it under the 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.
All the microscopic features described in this section are non-cancerous changes that support the diagnosis of a benign follicular nodule. However, they cannot be used to distinguish between specific conditions within the group.
Most patients with a diagnosis of benign follicular 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.