A 58-year-old woman underwent surgery and systemic chemotherapy(FOLFIRI plus panitumumab)for ascending colon cancer with multiple lymph node and liver metastases; the preoperative Virchow lymph node aspiration cytology showed adenocarcinoma.After 4 courses of chemotherapy, contrast-enhanced CT showed an embolus in the left subclavian vein.An anticoagulation therapy was started, but the embolus tended to increase.Three months later, the patient developed dyspnea and was diagnosed with pulmonary artery thromboembolism and superior vena cava thrombosis.Transcatheter examination was performed because of the anticoagulation-resistant embolism, and the biopsy revealed tumor embolism due to colon cancer.She died of respiratory failure 10 days after the biopsy.The tumor directly infiltrating the vein because of left subclavian lymph node metastases might have resulted from increased tumor emboli.Although cases of tumor emboli infiltrating the veins and developing from lymph node metastases are rare, a transcatheter biopsy may help to detect them.