INDUCED AND SPONTANEOUS THYROID CANCER IN THE SYRIAN (GOLDEN) HAMSTER12

Abstract

Twenty-four or 12% of 204 hamsters fed an iodine deficient diet of rice and carrots developed thyroid cancer with metastases to lymph nodes or lungs. An additional 57 or 28% had probable cancer and 121 or 59% had thyroid hyperplasia. Histologically, the cancers were follicular adenocarcinomas. For the most part, they were so well differentiated as to preclude a definite diagnosis of cancer in the absence of metastases. The well differentiated, metastatic cancers are comparable to the "metastasizing struma" of man. The neoplastic changes in the thyroid gland were diffuse, suggesting thyroid-stimulating hormone TSH stimulation. The findings were confirmed in a second experiment using hamsters from a different source. However, metastatic thyroid cancer was found only in females of this experiment. This could be a result of fortuitous selection or a manifestation of genetic differences. In other experiments, spontaneous thyroid cancer was found in 8 or 1.5% of 523 hamsters surviving 181 days or longer on a diet of Purina Laboratory Chow. The cancers were of two histologic types, papillary and follicular adenocarcinoma and spindle cell carcinoma. Lymph node metastases were found. The spindle cell type was the more frequent and is of particular interest because of the presence of nuclear inclusions in the spindle cells. Areas of the thyroid not involved with cancer were normal histologically. This suggests an etiologic mechanism other than that of TSH stimulation.