Thyrotoxicosis and thyroid cancer.

It is generally held that thyroid cancer is uncommonly associated with thyrotoxicosis. We report here nine patients with thyroid cancer amongst 720 patients with thyrotoxicosis. Three patients presented with features of malignancy together with thyrotoxicosis (Group A), one of whom had triiodothyronine (T3)-toxicosis. The remaining six patients were diagnosed following histological examination of tissues removed during subtotal thyroidectomies for hyperthyroidism (Group B). Two patients in Group A had follicular carcinoma; the rest were papillary in type. All the patients were rendered euthyroid initially, followed by ablative therapy for two patients in Group A and four patients in Group B. All but one are alive after one to nine years (mean of 3 . 4 years). The diagnosis of thyroid carcinoma is infrequently considered in the presence of thyrotoxicosis. The association is not clinically apparent in the majority of patients. The optimum management of such occult malignancies in thyrotoxicosis remains to be defined.