Lymphocytic infiltration surrounding liver metastases from colorectal cancer

Tumor infiltrating lymphocytes (TILs) have been recognized as a tumor-host reaction in various primary neoplasms. Although several studies reported TILs surrounding metastatic liver tumors, to the authors' knowledge few evaluations of the clinical significance of such features in patients with colorectal liver metastases have been carried out.

Forty-one patients who underwent initial hepatic resection for liver metastases from colorectal cancer were studied. Lymphocytic infiltration surrounding metastatic liver tumor was graded as weak or dense according to the mean number of TILs from 10 high-power microscopic fields (< or =50 or >50/HPF).

Dense lymphocytic infiltration between the metastatic tumor and hepatic parenchyma was seen in 18 of 41 patients (44%). Histologically, tumor invasion of the portal vein was rare in patients with dense TILs (12%) compared with patients with weak TILs (36%). Patients with dense TILs survived longer than patients with weak TILs after hepatic resection (P = 0.013). Multivariate analysis using the Cox proportional hazard model identified this pathological variable as a significant independent prognostic factor after hepatic resection.

The extent of lymphocytic infiltration between the metastatic nodule and hepatic parenchyma may reflect host defensive activity in the liver and is closely related to prognosis in patients who underwent hepatic resection for liver metastases from colorectal cancer.