Background: In colorectal carcinoma, venous invasion has been related to patient survival. Liver metastasis develops more frequently when venous invasion is present. However, the histologic features and clinical significance of venous invasion are not well understood.
Methods: A histologic study of venous invasion in colorectal carcinoma was performed on 19 patients with synchronous hepatic metastasis (Group A), 16 patients with metacaronous hepatic metastasis (Group B), and 26 patients with Dukes Stage C tumors who survived for 5 years without recurrence (Group C). The histologic features of venous invasion were classified into three types: tumor cells that were distant from the vein walls were categorized as floating type, those filling the lumen of a vein as filling type, and those surrounded by a vein obliterated with inflammatory reaction as occlusive type.
Results: Venous invasion was present in 89.5% of Group A patients and 75% of Group B patients, which was significantly higher than the 15.4% observed in Group C patients (P < 0.001). A slight to extensive degree of venous invasion was found in Groups A and B, but no extensive venous invasion was found in Group C. All patients in Groups A and B (except one patient) had floating, filling, or a combination of floating and filling types of venous invasion, whereas all patients in Group C had the occlusive type of venous invasion. A majority of the patients in all three groups showed invasion of extramural veins.
Conclusions: There is a close relationship between venous invasion and the development of liver metastasis in patients with colorectal carcinoma. Patients with no sign of metastasis had a lower incidence and lower extent of venous invasion, and inflammatory damage to the vein walls around the intravenous tumor appeared to reduce the likelihood of distant metastasis.