Intraatrial extension of thyroid cancer: technique and results of a radical surgical approach. An occlusion of the superior vena cava by a tumor thrombus extending into the right atrium was diagnosed in three patients with a follicular thyroid cancer. All patients showed the typical clinical picture of the superior vena cava syndrome. A right parasternal thoracotomy was performed for preparation of the major vessels. The superior vena cava was opened and the entire intravascular tumor thrombus was removed. The cavotomy was closed directly in two patients. In the third patient the left brachiocephalic trunk was resected and reconstructed with a vascular (polytetrafluoroethylene) graft. This patient had bone and brain metastases and an occlusion of the graft 3 months after surgery after anticoagulation was stopped. The other two patients were clinically symptom free without local recurrence 13 and 50 months after surgery. An aggressive surgical approach is justified in grossly invasive thyroid cancer to decrease local recurrence and death rates, to correct the disturbing clinical symptoms of superior vena caval occlusion, and to prevent tumor embolism and the development of distant metastases. By reducing tumor mass, an even better basis for radioiodine treatment can be prepared. 