Characteristics of thyroid cancer following irradiation

Studies in humans and animals have suggested that the distribution of histologic types of radio-induced thyroid cancers is different from that of naturally occurring tumors. In an attempt to verify that finding, histologic results of 31 patients with thyroid cancer, who had received irradiation to the head, neck or upper chest for other causes, were compared with those of 389 non irradiated patients. The two groups were homogeneous for age and sex. There was a significantly higher prevalence of the papillary type in the irradiated group, with an higher incidence of metastatic lymph nodes. Other histopathologic findings, coexisting with the papillary carcinoma (i.e., ground glass subtype, size less than 1.5 cm, multicentricity) did not differ significantly in the two groups. Some theoretical considerations concerning radio-induced thyroid carcinoma are proposed.