Abstract
Since the sixth edition of the General Rules for the Description of Thyroid Cancer published in September 2005, the rules have dealt with poorly differentiated thyroid carcinoma as an independent histologic type, namely, malignant neoplasms that are derived from follicular epithelial cells and show intermediate morphology and biological behaviors between well differentiated papillary carcinoma or well differentiated follicular carcinoma and undifferentiated carcinoma. Thereafter a total of 280 cases of thyroid carcinoma have been operated on in our department. Out of them four (1.4%) cases of poorly differentiated thyroid carcinoma were clinically studied. Two of the four patients were diagnosed with poorly differentiated thyroid carcinoma by fine needle aspiration cytology. Further these two patients presented clinical features suggestive of subacute thyroiditis and their tumors showed a rapidly increasing tendency in size. One of the two patients experienced early local recurrence and died of the disease nine months after the operation. In the remaining patient, complete resection of the tumor was impossible. Another two patients in whom poorly differentiated thyroid carcinoma was not diagnosed by fine needle aspiration cytology have been free from recurrence up to now. Poorly differentiated thyroid carcinomas have a variety of biological behaviors. There might be some tumors which have almost similar characteristics to undifferentiated thyroid carcinoma and the others which progress slowly and have similar characteristics to well differentiated carcinoma.
