Macroscopic features at the deepest site of tumor penetration predicting liver metastases of colorectal cancer.

Liver metastasis is the gravest prognostic factor in colorectal cancer. To identify a reliable indicator for liver metastasis, we evaluated macroscopic features and seven established histopathological findings at the cut section containing the deepest penetration using univariate and multivariate analyses in 417 colorectal cancers. Macroscopic features were divided into two types, streak type and non-streak type, according to the presence or absence of white streak(s) at the advancing margin of tumor invasion. Streak type was observed in 109 patients (26%). The frequency of liver metastasis in streak type tumors (56%) was significantly higher than that in non-streak type tumors (13%) (p < 0.001). The white streak corresponded histologically with cancer cells showing focal dedifferentiation with marked stromal and perivascular fibrosis extending towards the serosa or adventitia. In 343 curatively treated patients, univariate analysis showed that recurrent liver metastasis was significantly associated with macroscopic features, venous invasion, focal dedifferentiation and lymph node metastasis. Multivariate analysis disclosed that macroscopic features and lymph node metastasis were independent indicators of liver metastasis. These macroscopic features, corresponding histologically to stromal behavior against invading cancer cells, are a simple and useful indicator of liver metastasis of colorectal cancer.