Malignant Diseases of the Thyroid Gland*
Within recent years better understanding of malignant disease has brought the realization that the histologic morphology of the tissue is not always a criterion by which such growths may be differentiated or classified, and does not always indicate what may be their clinical course. This is particularly true of the malignant tumors of the thyroid gland, there being certain points in their origin, development, structure and growth characteristics which are just as important as their microscopic morphology and must be taken into consideration in order to distinguish the different types of growth and to understand the reasons for their peculiar variations. Therapeutic procedures should be planned on the basis of the growth characteristics of each different type-of neoplasm.
Development and Structure
The main body of the thyroid gland originates from an anlage in the primitive pharynx as an outgrowth of epithelial cells on its dorsal surface. Two lateral anlages also appear but are unimportant except as they may become aberrant thyroids. The anlage of the thyroid enlarges by progressive hyperplasia of the epithelial cells into a glandular arrangement to form the individually peculiar terminal compartments, or acini, which constitute the functioning part of the gland. No excretory ducts are formed. From the mesothelial bed of the primitive thyroid a fibro-elastic capsule and stroma develop to form septa which divide and subdivide the organ into lobes, lobules and a large number of terminal acinar vesicles. The glandular epithelium of the acini lies directly upon the connective tissue stroma, there being no. . .