Aims: Many studies have proven the importance of venous invasion in colorectal cancer with synchronous liver metastasis. The aim was to clarify the relationship between venous invasion and metachronous liver metastasis, which is not fully understood.
Methods and results: A histological study of venous invasion in colorectal carcinoma was performed using a total of 156 patients, of whom 52 survived without recurrence for 5 years (Group A); 47 had metachronous liver metastasis (Group B), and 57 had synchronous liver metastasis (Group C). The number and the maximum area of venous invasion were estimated in each case per x 40 field of cancerous lesions, which were divided into intramural and extramural lesions. A high incidence and high average number of foci of venous invasion appeared in Groups B and C. The average maximum areas of extramural venous invasion were much larger in Groups B and C than in Group A.
Conclusions: The average number of foci of venous invasion by colorectal cancer with metachronous liver metastasis did not differ significantly from that with synchronous ones. Furthermore, invasion into extramural large veins appeared to be associated with liver metastasis.