Tumor thrombus formation in the right common iliac vein after radical proctectomy in a patient with rectal cancer: a case report

BACKGROUND: Intravascular tumor thrombi are mainly found in patients with liver cancer or renal carcinoma but rarely occur in those with rectal cancer. CASE PRESENTATION: This is a case report of a 58-year-old woman with a swollen right lower extremity 14 months after radical resection for rectal cancer. Although ultrasonography indicated the presence of deep venous thrombosis (DVT) located in the right common iliac vein, interventional angiography showed that a circular mass, considered a tumor thrombus, was located in the right common iliac vein. The tumor thrombus was cured by interventional therapy, and the pathological report confirmed that the metastatic tumor thrombus originated from the rectal cancer. The patient underwent concurrent chemoradiotherapy and systemic therapy. However, right lung, retroperitoneum, and 2nd sacral vertebral metastases were discovered during follow-up. CONCLUSION: The correct diagnosis of a tumor thrombus and its differentiation from DVT can prevent incorrect treatment and prolong the survival of patients with rectal cancer.