Of the Origin, Characteristics and Behavior of Thyroid Cancer*

HISTORICALLY, positive identification of thyroid cancer has been characterized by a struggle with the pleomorphism of the tumors. Malignant neoplasms of the thyroid can resemble benign neoplasms or even normal thyroid architecture so closely that for many years the “benign” metastasizing goiter of Cohnheim (1876) (1) was believed to be a definite entity. This appeared to defy the laws of biologic behavior of malignant neoplasms. A modification of this concept occurred when Langhans in 1907 (2) described the condition as “proliferating goiter,” thus at least side-stepping a contradiction in terms. The confusion has been perpetuated by the relative infrequency of occurrence of thyroid cancer and by the long natural history of the less malignant phase of the disease. These two factors have contrived to limit observations on a sufficiently large number of patients over a period of time long enough to relate any of the histologic patterns (except the Group III cancers) with predictable behavior and prognosis. Even in the Group III cancers there are surprising exceptions.