Cancer of the thyroid gland has led to a great deal of controversy in the literature. There has been much disagreement as to incidence, classification, geographic relationship, diagnosis, and treatment of malignant disease of the thyroid gland.
The reported incidence of carcinoma of the thyroid varies from 1% to as high as 24%. This wide variation is largely due to 3 main factors—(1) the geographic location in which the survey of goiter is made; (2) the difference in the pathologic grading of carcinoma by microscopic change in the thyroid tissue, and (3) the manner in which various authors segregate the types of goiter from which cancer may arise. For example, the incidence of cancer developing in toxic diffuse goiter is very low (about 0.2%), the incidence in toxic nodular goiter is about 1%, while the reported incidence of cancer in nontoxic nodular goiter ranges from 6% to as high as