Medical literature contains numerous references to so-called "benign metastasizing goiter" and to "metastasizing normal thyroid tissue." Attention was first drawn to this condition by Cohnheim,1 who reported such a case in 1876. Many reports have since appeared. In 1926 Simpson2 reviewed the literature and collected 77 cases. Since that survey 28 additional cases have been reported in the literature.
The ability of tumors to metastasize at a distance has been generally considered a cardinal criterion of malignancy. Nevertheless certain primary benign neoplasms, chiefly those of connective tissue origin, such as lipomas, myxomas and chondromas, are capable of widespread dissemination. Generalization of benign epithelial tumors, on the other hand, rarely if ever occurs.
According to the literature, adenoma of the thyroid gland apparently forms an exception to the rule of nonmetastasization of benign epithelial tumors. Cases of simple adenoma, of hyperplastic goiter and even of normal thyroid tissue with