Local massive venous invasion in colorectal cancer: CT-pathological correlation and its clinical implication

Objective: To identify CT findings of massive venous invasion (MVI) in colorectal cancer, compare them to pathological findings and evaluate its clinical implications. Methods: Among 423 patients who received surgical resection of colorectal cancer, pre-operative CT of 26 patients (15 males, 11 females; mean age, 63.0+12.1 years) with histopathologially proven MVI and 26 patients (14 males, 12 females; mean age, 71.1+9.6 years) with histopathologically proven lymph node (LN) metastases were reviewed and compared with histopathological findings. We evaluated CT detectability of MVI and the morphologic differences between MVI and LN metastasis. All cases were followed up for at least 6 months after surgery. Results: Pre-operative CT correctly diagnosed only one case as tumour thrombus. 9 lesions were not detected on CT, and others were misdiagnosed pre-operatively as regional LN metastasis (14 cases) and juxtatumoural abscess (2 cases). After reviewing these cases, MVIs were identifiable in 20 of 26 cases. MVI was depicted on CT as nodules (oval, lobulated), abscess-like or intravenous tumour thrombus. MVI was significantly larger than LN metastasis (p < 0.05), while contrast enhancement was significantly lower (p < 0.05), and MVI often had an enhanced rim. Ten patients had synchronous metastases, and six patients had metachronous distant metastases within 5 years. Conclusion: Many cases of MVI were distinguishable from LN metastases on pre-operative CT of colorectal cancer, but their appearances were varied, reflecting their histopathological behaviours. The distant metastatic rate was much higher in cases with MVI. Advances in knowledge: Radiologists should be aware of CT findings of MVI in colorectal cancer as a sentinel sign of distant metastasis.