LAUSR

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. A total of 239 resection specimens were examined by tangential preparation of the extramural veins at the invasive tumor front. Average follow-up was 39 months. 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 of 29 patients in stage II and in 2 of 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 stages 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.