Anaplastic Thyroid Cancer
Fortunately rare, anaplastic is the most aggressive and most lethal form of thyroid cancer. The cause of the disease is unknown, but it has been associated with prior radiotherapy and rarely can arise from one of the differentiated thyroid cancers (papillary of follicular). Long term survival is uncommon (5 year survival of 5%) with most patients living less than a year after the diagnosis is made.
Signs and Symptoms
Anaplastic cancers typically progress rapidly creating a large mass in the thyroid which often causes compressive symptoms (difficult breathing, difficulty swallowing or voice changes). It is not unusual for this type of cancer to invade the surrounding structures such as the trachea or esophagus.
The diagnosis of anaplastic thyroid cancer often can be made on needle biopsy, but a larger sample is sometimes needed. Once the diagnosis is established, the patient requires imaging studies (CT scan of the neck and chest) to evaluate and stage the extent of the disease.
Patients with disease limited to the thyroid should undergo thyroidectomy. Unfortunately, this is only possible in a minority of patients. For patients with inoperable but localized disease, combined chemotherapy and radiotherapy can slow the progression of the disease in the neck. Unfortunately, distant metastasis invariably occurs at which point patients are treated with systemic chemotherapy, often in the context of a clinical trial.