The condition of an enlarged thyroid gland is commonly called “goiter.” A nodular goiter occurs when there is a nodule-like swelling in a part of the thyroid. Nodular goiters include benign and malignant tumors. Benign tumors include follicular adenoma, adenomatous goiter, thyroid cyst, and functioning nodules. Follicular adenoma is a true tumor, while adenomatous goiter is a condition in which thyroid cells proliferate and develop in a nodular form. Adenomatous goiter is actually a form of hyperplasia and not a clinical tumor. Adenomatous goiter or adenomatous nodules are more common than follicular adenoma.
- ◆Adenomatous goiter
- Adenomatous goiter is a condition in which thyroid cells proliferate (hyperplasia) and develop in a nodular form. The condition is also called adenomatous nodule if there is one or very few nodules present. However, it is very difficult to differentiate between the two types of nodules that arise from adenomatous goiter and follicular adenoma respectively. Adenomatous goiter is generally benign, but some lesions may contain cancer. Therefore, it is important to make an accurate diagnosis that distinguishes among conditions that appear similar.
- ◆Follicular adenoma
- The size of this type of nodule goiter varies from barely palpable to very large such that a patient cannot look down.
In extremely rare cases, functioning nodules produce excessive thyroid hormones, causing symptoms of hyperthyroidism similar to Basedow’s disease. This condition, toxic multinodular goiter, is called Plummer’s disease, named after the American doctor who first reported this disease. Although Plummer’s disease was thought to be rare in Japan, in recent years it has been detected more frequently due to advances in examination methods.
- ◆Thyroid cyst
- True cysts are, by definition, fluid or semi-fluid filled sacs. In reality, only a small proportion of thyroid cysts meets these criteria and can be called “true cysts.” Most thyroid cysts have other matter in them and are actually “cystic nodules” in which degeneration or bleeding in adenomatous goiter or follicular adenoma causes them to swell like a water balloon. For our purposes, since there are no clinical differences between true cysts and cystic nodules, both types are diagnosed and treated as cysts.