An electron-microscopic study of human thyroid cancer.

Authors studied the ultrastructural characteristics of the following thyroid cancer: papillary carcinoma, follicular carcinoma, undifferentiated carcinoma and medullary carcinoma. Some specific ultrastructural-functional correlations for each type of thyroid cancer could be established. Papillary and follicular carcinoma had some common features: larger nuclei than in benign lesions, a highly increased number of mitochondria, a reduced endoplasmic reticulum, cell junctions between the cells and an intact basal lamina. In addition, papillary carcinoma presented stage I and stage II nuclear inclusions, and nuclear invaginations that contained cytoplasm. The higher malignancy of follicular carcinoma compared with that of papillary carcinoma was assigned to less differentiated areas corresponding to the compact fields. Undifferentiated carcinoma consisted of large pleomorphic cells (spindle and giant cells) with abundant mitochondria, a flat rough endoplasmic reticulum, scanty secretory granules and lysosomes, cell junctions, all suggesting their common epithelial origin. Ultrastructure of medullary carcinoma contributed to the explanation of the amyloid origin and of granule types in correlation with hormone storage in cells.