Immunohistochemical study of colorectal cancer liver metastases: the immune/inflammatory infiltrate.

Our study is focused on the investigation of the immune/inflammatory infiltrate in liver metastases secondary to colorectal cancer. Twenty cases of colorectal liver metastases have been studied, including eight with recurrent metastases occurred after a previous treatment by thermonecrosis (group 1) and 12 with primary metastases treated exclusively by surgery (group 2). The cases were investigated by routine histopathological exam and by immunohistochemistry, using CD3, CD20 and CD68 antibodies. The design of the study envisages a comparative qualitative and quantitative evaluation of the B- and T-lymphocytes and macrophages inside the tumor and at the interface between liver parenchyma and tumor. Student's t-test was used for all statistical comparisons. The qualitative exam revealed, for both groups, the presence of an important T-lymphocyte, and respectively B-lymphocyte cell population at the interface between the tumor and the liver parenchyma, the number of intratumoral cells being extremely reduced. The statistical analysis showed significant differences (p<0.05 for groups 1 and 2, T- and B-lymphocytes, intratumoral vs. peritumoral). However, the comparison of group 1 with group 2 revealed no statistically significant differences between the mean value of intratumoral and peritumoral T- and B-lymphocytes, respectively. The qualitative exam revealed the presence of a well represented macrophage cell population, with a heterogenous distribution from case to case. This finding was confirmed by numerical information, with a lack of a statistically significant difference between the mean number of macrophages quantified intra and peritumoral, for both study groups. However, statistically significant differences were noticed between intratumoral and peritumoral mean value, respectively, for group 1 vs. group 2 (p<0.05). T-lymphocytes are the most numerous, their peritumoral location being the landmark for the histoarchitecture of the immune/inflammatory infiltrate and conducting the immune response developed at the interface between the tumor and liver parenchyma. The quantitative assessment of the immune infiltrate shows similar features in surgically resected metastases and recurrent metastatic disease after thermonecrosis. On the contrary, the quantitative evaluation of the macrophage population indicates a functional association rather with the primary metastasis process than with the recurrent metastatic disorder.