Aims Extramural venous invasion (EVI) is an important predictor of haematogenous metastasis in colorectal cancer (CRC). However, remarkable discrepancies in incidence rates indicate major problems regarding EVI assessment. The present prospective study applies tangential vessel preparation to CRC resection specimens and correlates results of EVI with metachronous haematogenous metastatic (MHM) spread.

Methods Stage II CRC diagnosed at the Institute of Pathology, University Teaching Hospital Feldkirch, Austria over a period of 30 months were analysed and tangential sectioning of the pericolonic tissue was performed. Confirmation, or exclusion of MHM, as assessed by computerised tomography, sonography or biopsy, was recorded.

Results In 50/79 (63%) cases EVI was detected. In 13/50 (26%), MHM developed. Of the 29/79 (37%) patients without EVI, only one (3.5%) developed MHM. Statistically, the rate of MHM for patients with EVI was independent of adjuvant chemotherapy.

Conclusions Tangential sectioning of the tumour periphery in CRC stage II yields a high rate of histologically evaluable extramural veins and permits proper assessment of EVI. Absence of EVI is significantly associated with metastasis-free survival, a finding of potential therapeutic value. On the other hand, one-third of the patients with EVI and circumferential tumour growth develop MHM, a setting in which the option for adjuvant chemotherapy should be considered. This study emphasises the importance of tangential sectioning of the invasive tumour front in CRC compared with the recommended perpendicular technique. The sensitivity and specificity of this method regarding MHM are characterised.