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.