Background Papillary thyroid carcinoma (PTC) often spreads lymphatically and direct vascular invasion leading to hematogenous spread is rare. We report a case of middle thyroid vein tumour thrombus in PTC. Case A 75-year-old female was referred to Endocrine Surgery for an incidental finding of a 22mm right thyroid nodule. Ultrasound-guided FNA confirmed PTC and she opted to undergo total thyroidectomy. Intraoperatively, a tumour thrombus was seen invading the middle thyroid vein. A 18F-FDG PET scan was concerning for possible low volume pulmonary metastasis. She underwent adjuvant I-131 radioactive iodine therapy. The initial ultrasound imaging was discussed with radiology retrospectively who advised it appeared suspicious for thrombus presence. Discussion Tumour thrombi are rare in PTC. A recent review identified 47 thyroid tumour thrombus cases in literature; only ten were PTC.[1] Ultrasound can identify tumour thrombi preoperatively, however, it is operator-dependent and detecting those located in the middle thyroid vein can be challenging. Thus, they can be missed in some cases. Conclusion The presence of tumour thrombi is associated with higher rates of recurrence and pulmonary metastasis, which represent two key challenges affecting outcomes in PTC. There is no standardised treatment approach for tumour thrombi in metastatic thyroid cancer, but it should not prevent aggressive surgical management. 1. Gui Y, Wang J-Y, Wei X-D. Middle thyroid vein tumor thrombus in metastatic papillary thyroid microcarcinoma: A case report and review of literature. World J Clin Cases. 2022;10(10):3213-3221. doi:10.12998/wjcc.v10.i10.3213