Medullary thyroid carcinoma in the Syrian golden hamster: an immunohistochemical study

Spontaneously occurring thyroid neoplasms exhibiting solid and/or anaplastic growth patterns in the Syrian golden hamster have been thought to be derived from follicular cells. Eight neoplasms of this type have been analyzed immunohistochemically and have been classified as medullary thyroid carcinomas (MTC) on the basis of their content of calcitonin (CT). Well differentiated MTCs in this species were composed of polyhedral cells showing uniform CT immunoreactivity while the poorly differentiated MTCs most often had spindle patterns of growth with marked variation in CT immunoreactivity. Both well and poorly differentiated MTCs contained entrapped follicles which were CT negative. In contrast to MTC in the rat and in humans with familial MTC, the tumors in hamsters were not associated with C-cell hyperplasia. The Syrian golden hamster may, therefore, serve as a useful model to study the factors which are responsible for the development of spontaneous (non-familial) MTC.