[Characteristics of the development of highly differentiated thyroid gland tumors].

Under study was the kinetics of morphological changes of high-differentiated carcinomas of the thyroid after repeat operative interventions, the interval between those was 2--15 years. It is suggested that during the development of high differentiated thyroid tumors the morphological structure of the tumor is remained and shows no tendency to transformation into anaplastic forms. Tumors showing both papillary and anaplastic structures (papillary polymorphous cancers) are considered to be the result of irregular tumor progression under which separate zones of neoplastic cells proved to be in different stages of differentiation.