Anaplastic Thyroid Cancer
Anaplastic thyroid cancer, also called undifferentiated thyroid cancer, is very rare and makes up only 1 to 2% of all thyroid cancers. Anaplastic thyroid cancer is more common in older people (with an average age of about 60) and is more common in women than in men. It is not known what causes anaplastic thyroid cancer, but often well-differentiated thyroid cancers can degenerate and turn into anaplastic thyroid cancer. The main risk factors for anaplastic cancer include an age greater than 65, history of radiation exposure to the chest or neck, and/or a long-standing goiter (i.e. enlarged thyroid). Unfortunately, anaplastic thyroid cancer is one of the most aggressive cancers in humans and is often lethal. Tragically, the five year survival from this type of cancer is less than 5%, with most patients dying within just a few months of the diagnosis. However, with new advances in treatment, there has been progress in helping patients with this disease.
Microscopic views of normal thyroid tissue versus anaplastic cancer
Signs and Symptoms
Unlike most thyroid cancers which do not cause symptoms, anaplastic cancers tend to grow very quickly (sometimes over a few weeks) and cause compressive symptoms which include difficulty swallowing, food or pills getting "stuck" when they swallow, and pressure or shortness of breath when lying flat. Patients typically notice a rock-hard mass they can feel or a visible mass (i.e. a mass they can see). In cases of advanced cancer that are growing (i.e. invading) into surrounding structures, patients may develop hoarseness or difficulty swallowing. Patients with compressive symptoms, enlarged lymph nodes, hoarseness, and/or a rapidly growing mass in the neck, especially if they have a known thyroid goiter, should seek medical evaluation right away.
Patients with a history of a rapidly growing neck mass with or without compressive symptoms should be evaluated immediately for anaplastic thyroid cancer. Other forms of thyroid cancer (especially medullary thyroid cancer) and thyroid lymphoma may present like anaplastic cancer. A FNAB can often distinguish between anaplastic cancer and another cause, but sometimes a core needle biopsy (i.e. biopsy with a large needle) or a surgical biopsy is necessary.
After the diagnosis of anaplastic thyroid cancer has been made, it is important to see how extensive the disease is. A CT scan of the neck and chest can show how large the tumor is, whether or not it is invading the nearby structures (muscles, trachea or esophagus), and can determine if the disease has spread to other parts of the body. A flexible laryngoscopy (scope inserted down the throat) can determine if the vocal cords have been affected by the cancer.
The best treatment for anaplastic thyroid cancer is complete surgical removal. Even those patients with potentially resectable disease will usually have invasion into surrounding structures like the windpipe, esophagus, large blood vessels, and often growth into the chest and complete resection is seldom possible. Patients with resected anaplastic thyroid cancer will likely need to join a clinical trial of chemotherapy and/or radiation therapy to further treat their disease. A small percentage of people with early stage disease that can be completely removed may live for many years after their diagnosis. However, most patients will have unresectable disease (i.e. cannot be completely removed surgically) at the time of diagnosis. For patients with unresectable disease, it is important to decide how best to improve the patient's quality of life and make their remaining days as comfortable and fulfilling as possible.
Some patients may be candidates for palliative surgery (i.e. treatment that is not curative but attempts to improve quality of life). This may include a tracheostomy tube (i.e. a tube through the skin into the trachea that helps them to breathe) and/or a feeding tube (i.e. a tube through the skin into the stomach through which they can be fed). However, some patients may choose to enter hospice care in which all therapies are aimed at making them as comfortable as possible for their remaining time.