Thyroid, Anaplastic Carcinoma
Anaplastic carcinoma of the thyroid (ATC) is the most aggressive thyroid gland malignancy. Although ATC accounts for less than 2% of all thyroid cancers, it causes up to 40% of deaths from thyroid cancer.
The aggressive nature of ATC makes treatment studies difficult to perform.
ATC generally occurs in people in iodine-deficient areas and in a setting of previous thyroid pathology (eg, preexisting goiter, follicular thyroid cancer, papillary thyroid cancer). Local invasion of adjacent structures (eg, trachea, esophagus) commonly occurs.
ATC has a rapid course and early dissemination. The most common sites of distant spread include (in descending order) lung, bone, and brain. Metastases (particularly in the lung) are likely to be present at diagnosis more than 50% of the time.
ATC comprises less than 2% of all thyroid malignancies. Fortunately, the incidence appears to be declining.
Worldwide frequency likely approximates that in the United States.
ATC typically has a rapidly progressive course. The overall 5-year survival rate is reportedly less than 10%, and most patients do not live longer than a few months after diagnosis.
The female-to-male ratio is approximately 3:1.
Peak incidence occurs during the sixth to seventh decades of life. The age range of affected patients reportedly is 15-90 years.
Patients with anaplastic thyroid carcinoma (ATC) typically present with a rapidly growing neck mass. Patients with metastases may also note bone pain, weakness, and cough. Neurologic deficits may be observed with brain metastases. The rapidly growing neck mass may produce the following symptoms:
Physical examination typically reveals a dominant neck mass. More than 40% of affected patients have lymph node enlargement, indicating local metastases. Pleural effusions may lead to decreased breath sounds on auscultation. With metastases, the physician may note bone pain and neurologic deficits.
ATC is believed to occur from a terminal dedifferentiation of previously undetected long-standing thyroid carcinoma (eg, papillary, follicular). ATC has a genetic association with oncogenes C-myc, H-ras, and Nm23.