THE FINE STRUCTURE OF THYROID TUMOURS INDUCED BY LOW IODINE DIET IN RATS

Triiodothyronine-secreting (toxic) adenoma of the thyroid gland: light and electron microscopic characteristics

A patient with thyrotoxicosis due to a triiodothyronine (T3)-secreting autonomous adenoma is described. The histmorphology of the neoplasms was similar to other neoplasms previously reported. Ultrastructural features of the adenoma are compatible with a very actively secreting follicular cell and are best compared with the ultrastructure of a diffuse toxic goiter. Distinctive features that separate toxic adenomas from various thyroid carcinomas and normal thyroid parenchyma are discussed.

Immunhistochemical and electron microscope analysis of adenomas of the thyroid gland. I. A comparative investigation of hot and cold nodules

Histologic, immunhistochemical and electron microscopic changes in 8 cases of scintigraphically proven autonomous thyroid adenomas are described and compared with non-functioning adenomas. Adenomas with a light microscopic appearance suggesting autonomy show follicles which are mainly small or normal sized and lined by columnar thyroid cells with a partly vacuolated and eosinophilic cytoplasm. Immunhistochemically a high content of thyroglobulin corresponds to the amount of rough endoplasmatic reticulum. Typical ultrastructural criteria are a well developed cytocavitary network, numerous mainly apically localized lysosomes, prominent Golgi fields with sprouting vesicles and autophagic vacuoles. The cell surface is, when compared to non-functioning adenomas, enlared apically by numerous long microvilli and basally by deep infoldings. On contrast to experimentally TSH-stimulated animal thyroids, colloid droplets and pseudopodia are rare. The morphological findings are compared with recent biochemical results and the diagnostic value of electron microscopy is discussed.

Transmission and scanning electron microscopy of experimentally induced thyroid tumors in rats

Irradiation of the neck region of 10 days old Wistar rats with 300 rads X-rays and their subsequent treatment with MTU leads to the development of thyroid tumors. The ultrastructure of the thyroid tumors induced was studied by transmission (TEM) and scanning electron microscopy (SEM). In follicular carcinomas, cylindrical or high columnar cells with abundant microvilli, well-developed ergastoplasmic reticulum and a hypertrophied Golgi complex predominate. The cytoplasm of the tumor cells of papillary carcinomas was composed of large pleomorphic cisternae, irregular in shape mitochondria, dense bodies, phagolysosomes and lamellar or multivesicular structures. Scanning electron microscopy revealed in the control animals a regular pattern of thyroid follicles tied to each other by tissue bridges and covered by set of blood and lymph vessels. The relief of the follicular carcinomas was irregular indicating follicles different in size and shape. The internal surface of the neoplastic follicles was also irregular as result of deep invaginations and intrafollicular cell growth. The apical region of the normal and neoplastic thyroid follicular cells was covered with abundant microvilli protruding into the colloid.