Distant metastases from thyroid and parathyroid cancer

Thyroid cancer represents a unique biological tumor where even with the hig h incidence of distant metastases, the overall prognosis is not as poor as many other human cancers. The overall long-term survival in patients presen ting initially with distant metastasis is approximately 50%. The overall in cidence of distant metastases varies between 10 and 35%, depending upon the histology. The overall incidence is directly related to various histologie s - being least in papillary thyroid carcinoma (10%) and highest in Hurthle cell tumor (33%). The incidence of distant metastases is also very high in patients with medullary and anaplastic thyroid cancer. The incidence of di stant metastases at the time of initial presentation in differentiated thyr oid cancer is approximately 4%. In high-risk patients - especially in patie nts with extrathyroidal extension or massive nodal metastasis - the distant metastases can be evaluated after total thyroidectomy with radioactive iod ine ablation. Pulmonary metastases are very common in young individuals, bu t they are extremely well treated and the mortality from distant metastases in this group is very low. However, distant metastases in patients with po orly-differentiated carcinoma have a poor prognosis. In high-risk patients, generally a total thyroidectomy should be undertaken so that the patient c an undergo radioactive iodine dosimetry and ablation as indicated. The surv eillance in patients with thyroid cancer includes: close clinical follow-up , chest X-ray, and radioactive iodine dosimetry. Thyroglobulin is commonly used as a prognostic marker in patients having undergone total thyroidectom y. The incidence of distant metastases in medullary thyroid cancer is high, mainly to the lung and liver. Persistent hypercalcitonemia is an indicatio n of regional or distant metastases. A variety of diagnostic tests are help ful, such as octreotide scanning, computed tomography scan, magnetic resona nce imaging and positron emission tomography scan. Laparoscopy to evaluate the surface of the liver is also an important investigation to detect dista nt metastases. The incidence of distant metastases is very high in patients with anaplastic thyroid Cancer, but most of the ti me the outcome depends on the locoregional recurrence and massive disease in the central compartme nt. The parathyroid cancer is quite rare, less than 1%, in patients undergo ing parathyroidectomy. The diagnosis of parathyroid cancer is made by patho logical features but the most certain method of diagnosis of a malignant tu mor of the parathyroid is the identification of secondary deposits. The inc idence of distant metastasis is difficult to determine due to the rarity of this condition, but the most common site is the lung. Patients with distan t metastasis have recurrent progressive hypercalcemia along with high parat hormone level. Copyright (C) 2001 S. Karger AG, Basel.