Tumor Thrombus of Thyroid Malignancies in Veins: Importance of Detection by Ultrasonography

Background: Tumor thrombus in the thyroid vein or the internal jugular vein may be caused by thyroid malignancies. Therefore, a tumor thrombus is very suspicious for malignancy. Total thyroidectomy should be performed in such patients if there is a primary thyroid tumor, and a high probability of pulmonary metastasis seems likely as there is direct exposure of malignant cells to the circulation. Our study was performed to determine whether ultrasonography is an effective preoperative modality to detect tumor thrombi of thyroid malignancies and whether tumor thrombi are associated with pulmonary metastases. Methods: Between 2004 and 2009, all thyroid surgery patients at Kuma Hospital had preoperative neck ultrasonography to look for tumor thrombi in the thyroid veins and the internal jugular veins as well as thyroid masses and abnormal lymph nodes. We looked for solid masses with an echogenic "tongue" in the internal jugular vein and masses with a projection from thyroid tumor to the thyroid vein on grayscale ultrasonography. We also used Doppler ultrasonography to look for the absence of blood flow. Results: Among 7754 patients who had thyroid surgery, there were 9 patients with tumor thrombi. In seven of the patients, tumor thrombi were detected by preoperative ultrasound, and in the remaining two patients, tumor thrombi were detected during surgery. Tumor thrombi were identified in the internal jugular vein in six patients and in the thyroid vein in three patients. Pulmonary metastases were present in three patients (50% of the patients with thyroid carcinoma). The patients with tumor thrombi were more likely (33.3%) to have pulmonary metastasis than those without (0.9%) tumor thrombi (p<0.0001). In four patients with papillary carcinoma, projection-like lesions of irregularly shaped tumors were misdiagnosed to be tumor thrombi in the thyroid veins on preoperative ultrasound. These four patients did not have pulmonary metastases. Conclusions: The preoperative detection of a tumor thrombus on ultrasonography has important clinical significance. Therefore, preoperative neck ultrasound in patients with thyroid masses should attempt to determine whether there are signs of tumor thrombi as well as to characterize the nature and location of abnormal thyroid and extrathyroid masses.