Two major factors affect thyroid cancer survival. The first is the type of thyroid cancer present in the patient. Thyroid malignancies arising from different tissues have very different prognoses. The second major factor affecting survival is how far the cancer has progressed at the time of diagnosis. Disease that has spread throughout the body is much harder to eradicate than localized disease.
Perhaps the most important factor affecting thyroid cancer survival is the variety found in the patient. Identifying the type of thyroid cancer present depends on a number of investigative studies because the appearance of the lump found on physical examination of the thyroid is a nonspecific sign that does not point to a specific cancer. Often, an ultrasound imaging study, which uses sound waves to evaluate underlying structures, provides clues regarding the type of thyroid cancer present. Final determination of the cancer subtype often relies on examination of a sample of the mass by microscope.
Fortunately, the most common type of thyroid cancer is also the type with the best prognosis. Papillary adenocarcinoma, also called papillary thyroid cancer, accounts for over 70 percent of thyroid cancer diagnosed in adults and children. The five-year survival for this type of cancer is over 95 percent.
Follicular carcinoma of the thyroid has an intermediate prognosis. It spreads more easily than papillary thyroid cancer because it invades blood vessels, and can travel to distant locations. Five-year survival rates are approximately 90 percent.
Thyroid cancer survival rates are decreased in some other, rarer varieties. Medullary thyroid cancer is often associated with certain genetic conditions, and is typically difficult to treat. Anaplastic thyroid cancer generally affects older women, grows rapidly, and has high mortality rates. Lymphoma of the thyroid can also be seen in some cases, and the prognosis for this disease is poor.
Another important factor that influences thyroid cancer survival is how extensive the disease is at the time of diagnosis. Patients with a small mass that has not invaded outside of the thyroid have the best prognosis. Other cancers that have grown throughout the thyroid and have infiltrated surrounding structures are harder to treat, and are associated with a worse prognosis. Thyroid malignancies can spread to the lymph nodes through the lymphatic system, and patients who have cancer in nearby lymph nodes also fare poorly. The worst prognosis is typically reserved for the patients who have metastatic cancer, which means that the cancer has spread into the blood and started to grow in distant organs.