The Comparative Pathology of Cancer of the Thyroid, with Report of Primary Spontaneous Tumors of the Thyroid in Mice and in a Rat: Studies on the Incidence and Inheritability of Spontaneous Tumors in Mice XXII

The malignant tumors of the thyroid in man are observed with greatest frequency in districts where goiter is most often seen, as if the proliferative activity of goiter predisposed to malignant proliferation. Therefore, we find many reports of cancer in the goitrous districts of Switzerland, Kocher (1) especially having observed many cases, reporting finding 311 cases of thyroid cancer among 3,500 cases of goiter, a frequency of thyroid cancer probably not paralleled in other parts of the world. Wilson (2) reports that among 16,549 cases of simple and exophthalmic goiter operated upon in the Mayo Clinic 207 were malignant, and there were also 83 cases of thyroid malignancy in an inoperable state. In the lower animals few cases of malignant disease of the thyroid have been described except in dogs, in which species goiter is extremely common. Here in Chicago it is difficult to find a normal thyroid in an adult dog, and Marine (3) reported that examination of 202 dog thyroids obtained in Cleveland disclosed but 19 that were histologically normal, although none showed malignant changes. Of 15 old dogs examined by Good-pasture and Wislocki (4), all of which showed some sort of tumor or tumor-like growth, five had benign nodular growths in the thyroid.