THYROID NODULES

FINE NEEDLE ASPIRATION BIOPSY

Thyroid nodules are thyroid lumps found in approximately 5% of the population at palpation screening, and is almost 7 to 8-fold more frequent at ultrasonic screening. Thyroid nodules are rare in children and adolescents and increase almost linearly with age; females are affected 2 to 4 times more frequently than males. Nodular thyroid disease is a heterogenous disorder with regard to clinical, functional or histological aspects: nodules may be single or multiple, hyper- or hypo-functioning, benign or malignant. Malignant nodules account for roughly 10% of all nodules. The large majority of these arises from the follicular epithelium and includes well-differentiated carcinomas in 75% of cases and poorly differentiated or anaplastic in 15% of cases. Medullary cancer arising from calcitonin-producing parafollicular cells account for approximately 10% of cases.

Important facts about thyroid nodules

Simply put, thyroid nodules are lumps which commonly arise within an otherwise normal thyroid gland. Often these abnormal growths of thyroid tissue are located at the edge of the thyroid gland so they can be felt as a lump in the throat. When they are large or when they occur in very thin individuals, they can even sometimes be seen as a lump in the front of the neck. The following is a list of facts regarding thyroid nodules:
 

• One in 12 to 15 women has a thyroid nodule
• One in 40 to 50 men has a thyroid nodule
• More than 90 percent of all thyroid nodules are benign (non-cancerous growths)
• Some are actually cysts which are filled with fluid rather than thyroid tissue

Three questions 

1. Is the nodule one of the few that are cancerous?
2. Is the nodule causing trouble by pressing on other structures in the neck?
3. Is the nodule making too much thyroid hormone?

These questions can be answered after your endocrinologist performs some tests. These include blood tests for thyroid activity, an ultrasound scan to study the nodule, and a biopsy.

Early diagnosis and treatment is important to reduce thyroid cancer mortality. However since malignant nodules are a small minority, to directly operate on all nodules is impractical, cost-ineffective and would expose people with benign nodules to unnecessary risks.

Fine needle aspiration biopsy (FNAB), also called fine needle aspiration cytology (FNAC), of the thyroid was first described in 1948. It gained widespread use since the 1970s, and is an accurate and useful diagnostic procedure for distinguishing benign from malignant thyroid nodules. The routine use of FNAB has allowed doctors to spare patients from unnecessary operations for benign nodules and reduce costs of care.

FNAB is usually carried out in an outpatient setting. It is virtually painless and free of major complications. The patient lies on a couch with a pillow under the neck to relax the neck muscles. The nodule is identified by palpation or ultrasound. A very fine needle is inserted and then moved back and forth to obtain thyroid material. Local anaesthesia is given prior to biopsy. To increase cellular yield it may be necessary to perform 3 to 5 aspirations. The material is then smeared onto glass slides and stained with special dyes. The slides are then examined under a microscope. A cytopathologist (specialist in studying cells for cancerous features) will do a careful study of the slides. Results are usually available in 1 to 2 work days. After the FNAC, the patient will be allowed to go home. The whole procedure usually takes no more than 30 minutes. Most patients do not experience any problems after the biopsy. A few minority may experience some soreness and bruising in the thyroid area. Analgesic medication will be given and if necessary, medical leave.

Treatment

If the nodule is not cancerous and is not causing any symptoms, it may be left alone. Surgery is not necessary. Benign nodules do not turn into malignant ones over time.

If thyroid cancer is indeed discovered, you need to be treated. There are over 11,000 new cases of thyroid cancer each year in the United States. Females are more likely to have thyroid cancer at a ratio of three to one. Thyroid cancer can occur in any age group, although it is most common after age 40, and its aggressiveness increases significantly in older patients. The majority of patients present with a nodule on their thyroid which typically does not cause symptoms.

Thyroid cancer

Most thyroid cancers are very curable. In fact, the most common types of thyroid cancer (papillary and follicular) are the most curable. In younger patients, both papillary and follicular cancers can be expected to have better than 95% cure rate if treated appropriately. Both papillary and follicular cancers are typically treated with complete removal of the lobe of the thyroid which harbors the cancer, PLUS, removal of most or all of the other side.

Medullary cancer of the thyroid is significantly less common, but has a worse prognosis. Medullary cancers tend to spread to large numbers of lymph nodes very early on, and therefore requires a much more aggressive operation than does the more localized cancers such as papillary and follicular. This cancer requires complete thyroid removal PLUS a dissection to remove the lymph nodes of the front and sides of the neck.

The least common type of thyroid cancer is anaplastic which has a very poor prognosis. It tends to be found after it has spread and is not cured in most cases. Often an operation cannot remove all the tumor.

Thyroid cancer is unique among cancers, in fact, thyroid cells are unique among all cells of the human body. They are the only cells which have the ability to absorb iodine. Iodine is required for thyroid cells to produce thyroid hormone, so they absorb it out of the bloodstream and concentrate it inside the cell. Most thyroid cancer cells retain this ability to absorb and concentrate iodine. This provides a perfect "chemotherapy" strategy. Radioactive iodine is given to the patient and the thyroid will absorb and concentrate it. Since all other cells of our bodies cannot absorb the toxic iodine, they are unharmed. The thyroid cancer cells, however, will concentrate the poison within themselves and the radioactivity destroys the cell from within. No sickness. No hair loss. No nausea. No diarrhea. No pain.

Not all patients with thyroid cancer need radioactive iodine treatments after their surgery. This is important to know. Others, however, should have it if a cure is to be expected. Your endocrinologist will advise you about what treatment is best for you. Following treatment you need to taking thyroid hormone and maintain followup for life.