Thyroid cancer is a disease that spans all age groups and it is currently the fastest-growing cancer in America. The American Society of Clinical Oncology estimates that 56,460 adults in the United States (13,250 men and 43,210 women) will be diagnosed with thyroid cancer this year. How much is due to an increase in surveillance or screenings and how much is due to a biological change in disease prevalence is uncertain. The lack of symptoms also means that, in some cases, the disease progresses to advanced stages before people are aware they have a thyroid problem.
Several types of thyroid cancer exist, some behave more aggressively than others. The most common type is Papillary Thyroid Carcinoma (PTC). PTC represents approximately 60% of thyroid cancers, the others being follicular, medullary, insular and anaplastic. For the most part, with some exceptions, thyroid cancers are slow growing and metastasize to regional lymph nodes in the head and neck.
Ultrasound features of PTC include indistinct borders, a heterogenous echogenicity and microcalcifications can also be seen. From a cell perspective, the diagnosis of papillary thyroid carcinoma can be made on fine needle aspiration biopsy, and aspirate is usually very cellular. The cells exhibit very specific cytologic characteristics, which reflect the genetic mutations that have occurred to cause the cancer in the first place. Intranuclear inclusions are seen in some smears and are a cytologic reflection of the membrane disruptions that are caused by the RET/PTC oncogene mutation.
The first indication of thyroid cancer is the discovery of a lump in the neck within the thyroid gland, but many times a nodule escapes physical examination and is found incidentally. Once a nodule is detected, the diagnosis is often determined by an ultrasound-guided fine needle aspiration. Additional testing of the cells removed from an aspiration procedure may reveal disruptions on the molecular level that may be indicators not only of the type of thyroid cancer that is being dealt with, but also may be predictors of the behavior of the cancer (i.e. whether or not it is likely to metastasize or recur after treatment).
Cancers from other areas of the body have also been known to metastasize to the thyroid gland. I have seen cases of renal (kidney) carcinoma, squamous carcinoma and breast cancer all find their way to the thyroid gland. Lymphomas are also known to occur in the thyroid.
Certain populations of patients have a predisposition to thyroid cancer. People who have had exposure to radiation, especially children who receive radiation treatments to the head and neck or for diseases such as lymphoma, Wilms tumor or neuroblastoma, are at risk. People outside the United States who have a diet low in iodine are at risk for certain thyroid cancers (follicular and papillary). In the US, iodine is added to table salt and other foods. Medullary thyroid carcinoma is associated with “Multiple Endocrine Neoplasias”, a group of genetic disorders where tumors are found in the endocrine glands, including thyroid, adrenal, pituitary and parathyroid glands. Family history, especially a first degree relative with thyroid cancer, is also a risk, even though most people who develop the disease do not have a family history or genetic predisposition to it. Finally, thyroid cancer occurs 3 times more often in women than in men.
For more information about thyroid cancer and to support thyroid cancer awareness, visit the Thyroid Cancer Survivors’ Association website at www.thyca.org