According to Ewing,1 the occurrence of true sarcoma of the thyroid gland still requires demonstration, and in a review of the literature it is quite evident that tumors of the thyroid have been classified as sarcoma merely because of the presence of spindle cells or round cells without the application of any more accurate criteria of diagnosis. Since the age of incidence, clinical course, gross anatomic appearance and mode of extension are quite similar in carcinoma and sarcoma of the thyroid, only the histologic distinctions between the two remain. Confusion in microscopic diagnosis frequently occurs owing to the fact that.it has not been fully appreciated that the cells of a carcinoma of rapidly proliferating type assume an undifferentiated form superficially resembling in morphology the cells of a fibrosarcoma or lymphosarcoma; unless the arrangement of the cells is carefully studied in various parts of the tumor and special staining methods