Endocrine Abstracts

Introduction: The occurrence of thyroid cancer in Basedow disease is rare. We report a series of five cases of patients with Basedow disease who were operated on and whose pathological examination showed an association with differentiated thyroid cancer.

Clinical cases: We report a series of five patients with a mean age of 39 years. The diagnosis of Basedow disease was made on the basis of clinical, biological and scintigraphic evidence. Cervical ultrasound showed a benign multiheteronodular goitre in four patients, while thyroiditis with a nodule classified as EU-TIRADS V was present in one patient. All patients underwent total thyroidectomy after medical preparation with synthetic antithyroid drugs. However, one patient underwent central lymph node dissection. Histology was consistent with papillary thyroid carcinoma in four patients and vesicular carcinoma in one patient. Four patients classified as low-risk received 100 mci isotope totalization and TSH- suppressive Levothyroxine therapy, while one patient classified as very low-risk received TSH- suppressive Levothyroxine therapy alone. All clinical cases were in remission.

Discussion: The association of thyroid carcinoma with Basedow disease, once considered antinomian, is now a proven but rare occurrence. The incidence of differentiated thyroid carcinoma in Basedow disease is usually between 2 and 10%. Papillary carcinoma is the most frequently found. Nodularity should suggest Basedow disease -associated carcinomas. The pathogenesis of this association remains poorly understood. Studies have shown that anti-TSH receptor antibodies can stimulate adenyl cyclase activity and induce the formation and growth of thyroid cancer. In addition, the influence of synthetic antithyroid drugs can normalise the level of TSH that is inhibited in hyperthyroidism, with the risk of growth of a previously occult tumour. The most frequent situation is juxtaposed hyperthyroidism, resulting from healthy thyroid tissue adjacent to the cancer. These observations underline the importance of a careful search for malignancy in nodules associated with Basedow disease.

Conclusion: The diagnosis of Basedow disease does not eliminate the possibility of associated thyroid cancer. Thus, the appearance of a nodule within the goitre should raise suspicion of malignancy and indicate radical surgical treatment. Our results suggest a good prognosis for differentiated carcinomas on Basedow disease with isotopic totalisation.