Histopathological evaluation of resected colorectal cancer liver metastases: what should be done?

Histological reporting of hepatic resections of colorectal liver metastases (CRLMs) is limited to confirmation of diagnosis and evaluation of resection margins. More exhaustive diagnostic reporting might be warranted. Here, we critically and systematically review the potentially important histological prognostic factors in CRLM. Histological features such as intrahepatic spread, resection margins, and tumour response to neoadjuvant chemotherapy have been defined. Intrahepatic spread (venous, lymphatic, bile duct and perineural invasion) was evaluated in a number of studies. Meta-analysis demonstrated a clear correlation between 5-year overall survival and both portal vein invasion (RR 1.8, 95% CI 1.3-2.5) and lymphatic invasion (RR 1.7, 95% CI 1.4-2.0). The impact of hepatic vein invasion and bile duct invasion on outcome is not clear. Perineural invasion was linked to survival in one study. Resection margin is an important prognostic factor; however, the significance of the width of negative margins remains controversial. Various studies have evaluated tumour response to neoadjuvant chemotherapy, but different grading systems were used, and definite recommendations cannot be made. In conclusion, with the high incidence of CRLM and the increase in the number of hepatic resections, we need well-defined prognostic factors, studied in homogeneous patient populations, to optimize diagnostic work-up. This review identifies several of these factors.