Cancer is a disease that will strike a large number of individuals. As such, it is important for a health care provider to understand the steps in its development. The annual incidence of thyroid cancer is approximately 60,000 cases. There are approximately 2,000 annual deaths from it. There are four principal types of this cancer. They are papillary, follicular, medullary and anaplastic. The cancers are typed based upon their cell pathology (National Institutes of Health, 2014). The various steps of cancer development include initiation, promotion and progression. Once cancer develops, it is then traditionally staged in levels from one to four. However, this depends upon the type of cancer. Lymphomas are not staged in this manner. Thyroid cancer is recognized to have the four traditional stages.
Initiation involves the mutation of the cell’s DNA. At this point, the mutation may or may not be harmful to the individual. The next stage is promotion. During this stage, the mutated cell is encouraged to replicate into daughter cells. All of these daughter cells will possess the mutated DNA. The last stage is progression. In this stage, the mutated cells progress to cancer (Cancer Quest, 2013).
Once cancer develops in an individual, there are usually four stages associated with its growth. Thyroid cancer is staged according to the TNM staging system. T refers to the size of the tumor. N refers to its spread to regional lymph nodes and M refers to its metastasis. These stages are then further broken down. Stage T may be broken down into stages X through 4b. In stage X, the primary tumor cannot be sized. By stage T4b, the tumor has reached the spine or spread into nearby blood vessels. This stage is also called “advanced early disease.” In Stage N, lymph nodes are also involved. This is staged from NX to N1b. In NX, the lymph nodes cannot be assessed. In Stage N0, the cancer has spread to nearby lymph nodes. The lymph nodes near the thyroid are staged as N1a. The cervical lymph nodes are involved by the stage N1b. In metastasis, stage M0 indicates there is no metastasis. In stage M1, the cancer has spread to distant parts of the body (American Cancer Society, 2013).
The traditional stages which most people are familiar with are Stages 1 through 4. This is a simpler method to stage cancers, but follows the basic premise of the TNM system. In Stage 1, the tumor is limited to the thyroid and is less than 2 cm in size. In Stage 2, it is has grown in size greater than 2 cm. In Stage 3, the cancer has spread to the nearby lymph nodes. In Stage 4, the cancer has metastasized to distant body regions (Thyroid Cancer Survivor’s Association, 2013).
There are several requirements for the tumor to advance. In local extension, the tumor has begun to move past the original boundaries. As a tumor grows, it requires its own blood supply. This is referred to as angiogenesis. Tumor angiogenesis begins when the cells of the tumor send out chemical messengers indicating that it requires a blood supply. These messengers work on the cells of the nearby tissues and organs. The nearby tissues and organs respond by activating genes that can create blood supplies. This is called angiogenesis. The tumor then has its own blood supply to feed it with nutrients and oxygen. The blood supply can also remove waste products from the tumor. This allows the cancer to also move into the blood vessels. It is now understood that angiogenesis is an important part of the spread of cancer. If angiogenesis stops, the growth and spread of the tumor will also stop. The tumor must spread through the detachment of cells from the primary tumor. These are then spread through the extracellular matrix. They then spread through the blood stream and must undergo extravasation from the blood supply. This allows them to adhere to the parenchyma of the target organ. At this point, the cells can then begin to colonize on the organ. This is metastasis of the cancer (Miles, Pruitt, van Golen, & Cooper, 2008, p. 305).
- American Cancer Society. (2013, January 17). How is thyroid cancer staged? Retrieved March 17, 2014, from: http://www.cancer.org
- Cancer Quest. (2013). Cancer initiation, promotion and progression. Winthrop Cancer Institute. Retrieved March 17, 2014, from: http://www.cancerquest.org
- Miles, F. L., Pruitt, F. L., van Golen, K. L., & Cooper, C. R. (2008). Stepping out of the flow: capillary extravasation in cancer metastasis. Clinical & experimental metastasis, 25(4), 305-324.
- National Institutes of Health. (2014). Thyroid cancer. Retrieved March 17, 2014, from: http://www.cancer.gov
- Thyroid Cancer Survivor’s Association. (2013, April 23). Thyroid cancer: types, stages and treatment overview. Retrieved March 17, 2014, from: http://www.thyca.org