Prognostic significance of intratumoral natural killer cells in primary resected esophageal squamous cell carcinoma

Background: Natural killer (NK) cells are important effector cells in the defense against tumors. The present study retrospectively examines the intratumoral NK cells in primary resected esophageal squamous cell carcinoma (ESCC) and the correlation between the patient' outcome and the intratumoral NK cells infiltration. Methods: Immunohistochemistry was used to analyze the intratumoral NK cell infiltration in 38 archival specimens from patients with primary resected ESCC. Results: According to the cut-off point of the staining for intratumoral NK cell infiltration, 14 (37%) cases had high level infiltration and 24 (63%) low. The 5-year survival of patients with high level NK infiltration was significantly better than that of patients with a low level of NK infiltration (p < 0.01). Multivariate analysis did not show NK cell infiltration to be a significant prognostic factor. Conclusions: Intratumoral NK cell infiltration is associated with a favorable outcome in ESCC. Intratumoral NK cell infiltration might be used as a variable with prognostic value in primary resected ESCC.