Background & Aims: Microvascular invasion (mVI) has repeatedly been correlated with recurrence and survival after liver transplantation (OLT) for hepatocellular cancer (HCC). A grading system to predict the risk recurrence of HCC based on histological features of mVI has already been developed for resection but not for OLT.

Methods & Patients: We reviewed all cases of OLT for pathology proven HCC from 1/1/00 – 12/31/09. All specimens were re-reviewed to corroborate extent of vascular invasion as none, microscopic or gross. Those with mVI were further examined to determine the # and size of vessels invaded by tumor cells, the presence of a muscular wall around the vessel, and furthest distance of mVI from the tumor. The highest # of tumor cells within a vessel was also recorded for each case. Clinical variables such as tumor size, number, grade, Milan criteria and AFP were also examined. Primary endpoints were recurrence and survival.

Results: During this period, 409 patients underwent OLT for HCC – 232 with no invasion, 139 with mVI, and 38 with gross invasion. Median follow-up was 33 mo. There were 62 deaths and 34 recurrences in the mVI group. Median and 5 year survivals were 69 mo. and 53% for the mVI group. Recurrence rate at 5 years was 33% for the mVI group. Multivariate analysis revealed that Milan criteria, tumor grade and # of cells invading a vessel (cut-off 100 cells) independently correlated with recurrence in patients with mVI. Only # of cells invading a vessel was found to independently correlate with survival. See table:

Conclusions: mVI encompasses a heterogenous population of patients with a wide range of potential outcomes. The burden of tumor cells invading microscopic vessels can independently stratify patients in terms of both recurrence and survival.

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