Incidence of extramural venous invasion in colorectal carcinoma as determined at the invasive tumor front and its prognostic impact.

Extramural venous invasion (EMVI) is prognostic for colorectal cancer, however veins are only detected partially by normal perpendicular preparation. Therefore reported findings are conflicting and standardization is required. 239 resection specimens were examined by tangential preparation of the extramural veins at the invasive tumor front. Average follow up was 39months. The relationship of EMVI to metachronous hematogenic metastasis (MHM) was evaluated. With this method, a high prevalence of EMVI beginning in stage II is apparent. In stage I, 66% of patients with EMVI developed MHM, in stage II 25%, and in stage III 49%. In stage III the number of tumor-invaded veins is crucial. In the absence of detection of EMVI, MHM occurred in 1/29 patients in stage II, and in 2/13 patients in early stage III. By tangential sectioning at the invasive tumor front we found a high incidence of EMVI beginning in stage II, which increases with tumor stage. Especially in stage II and III, the correct determination of absent EMVI has a high negative predictive value for MHM. In stage I EMVI defines a patient group with increased risk for MHM. The quantification of EMVI is an important issue for standardization.