The anaplastic transformation of differentiated thyroid carcinoma. An ultrastructural study.

The authors studied 60 thyroid carcinomas (29 folliculo-papillary carcinomas, 20 follicular carcinomas and 11 undifferentiated carcinomas), using ultrastructural, morphometrical and immunohistochemical methods. The anaplastic transformation correlates with the following aspects: decrease of intercellular junctions and of microvilli together with alteration of cell organelles. Immunohistochemically, thyroglobulin is present in various amounts in differentiated carcinoma, but it is absent in undifferentiated tumors. A good correlation is found between the pattern of thyroglobulin and the ultrastructural aspects of neoplastic cells. The authors consider that anaplastic tumors originate from differentiated carcinomas. The decrease of junctions, the modifications in the number and shape of microvilli, the alterations of cell organelles and the changes of thyroglobulin pattern are the principal parameters involved in the anaplastic transformation. These criteria can be also used in order to ascertain an early diagnosis in the thyroid carcinoma evolving anaplastic changes.