Hyperthyroidism in a Patient With Anaplastic Thyroid Cancer

Abstract

Anaplastic thyroid cancer (ATC) is one of the most lethal tumors in human medicine; it is characterized by aggressive local invasion and rapid appearance of distant metastases. Tumor compression on surrounding structures in the neck results in symptoms which dominate the clinical presentation. Hyperthyroidism is an extremely rare clinical feature in ATC which is the consequence of normal thyroid follicle destruction caused by tumor invasion. When the tissue destruction is complete, the hyperthyroid phase is followed by the hypothyroid phase of the disease. Such clinical presentation resembles various thyroiditises, thus the name "malignant pseudothyroiditis" or "anaplastic pseudothyroiditis." This is a case report of a 67-year-old man, with concurrent development of ATC and clinical thyrotoxicosis. Despite administration of the antithyroid drugs and ␤-blockers, surgical tumor reduction and adjuvant radiotherapy, the patient died 5 months after the onset of the disease. The literature referring to previous cases of ATC with thyrotoxicosis is reviewed.