Diagnosis of Thyroid Cancer
A diagnosis of thyroid cancer usually involves taking a complete family and personal medical history and performing a physical examination of the neck area to check for unusual growths or swelling in and around the thyroid gland and lymph nodes. Patients may be referred to a doctor who specializes in the diagnosis and treatment of disorders of the endocrine system (an endocrinologist).
Blood tests may be recommended to check the levels of certain hormones in the blood. The level of thyroid stimulating hormone (TSH) in the blood can provide valuable information about how well the thyroid gland is functioning and the level of calcitonin in the blood may indicate medullary thyroid cancer.
Thyroid enlargement (goiter) is cancerous in less than 5% of cases. To help make a definitive diagnosis, physicians may use the following tests:
Although an ultrasound cannot give the definitive diagnosis, it can help show if there are signs that indicate whether a nodule is problematic or not. For example, if the ultrasound shows that the nodule has clearly defined and symmetrical edges, is fluid filled, and does not have blood flowing through it, chances are it is benign. If an ultrasound does reveal any unusual signs, then a biopsy will most likely be recommended. Ultrasound is a quick, painless and non-invasive procedure that uses sound waves to create an image of the nodule, which is then examined on a monitor.
The most definitive test for signs of malignancy is often a fine-needle biopsy. During this test, the doctor uses a fine-gauge needle to remove small samples of cells, which are then examined under a microscope by a pathologist. This test can usually be performed in the doctor's office and may or may not require local anesthesia. Samples are taken from several areas within each nodule. An ultrasound may be used to help identify nodules that are too small to be felt by hand through the skin.
If a definitive diagnosis cannot be made with a fine-needle biopsy, a surgical biopsy will need to be performed. This procedure is done in an operating room under general anesthesia.
This test (also called thyroid scintigraphy), although not definitive, can be used to help evaluate how the cells within a nodule are functioning. Follicle cells within the thyroid gland take up iodine. The cells in most benign nodules and almost all malignant nodules take up less iodine than surrounding healthy thyroid tissue. In this procedure, radioactive iodine is given orally or by injection. If the cells within the nodules take up the radioactive iodine, they can be detected using a specialized camera. These nodules are referred to as "hot," but are almost never malignant. However, cells that do not take up the radioiodine are referred to as "cold"—and these cells could be benign or malignant.
Staging refers to a system that helps determine how far a cancer may have spread. Proper staging helps determine the treatment process. That is, determining the stage of the thyroid cancer is key to choosing the most effective treatment options. Roman numerals from I-IV (i.e., one to four) are used to describe how far a cancer has progressed. The stages are based on an assessment called the TNM system.
The letters TNM refer to:
- tumor size (denoted by T);
- spreading to the lymph nodes (denoted by N);
- spreading to other areas in the body, called metastasis (denoted by M).
For example, a diagnosis of "T1, N1, M0" refers to a tumor that is smaller than one inch (T1), with some lymph nodes affected (N1), and no metastasis (M0). This diagnosis would likely be considered "stage I" thyroid cancer.
The diagnostic methods outlined previously help determine the staging. Tumors (T) and lymph nodes (N) can be staged during removal surgery or by the use of ultrasound, CT scan, or MRI. The spread, or metastasis (M), of thyroid cancer is measured by using radioactively tagged iodine (or a hormone in the case of medullary thyroid cancer) and scanning the body with a special camera that can detect where the cancer has spread.