CD68 and hepatocellular carcinoma: There was a significant positive correlation between CD68, iNOS and CD163 expression and diethylnitrosamine treatment time in the primary rat HCC model (r = 0.09, p = 0.01; r = 0.21, p < 0.0001; r = 0.60, p < 0.0001; respectively) (Additional file 1: Fig. S4B-D).