['Chemotherapy has been shown to induce apoptosis in esophageal cancer. However, no windows of opportunity exist to selectively kill tumor cells without killing host cells. Due to the concern that tumor-infiltrating lymphocytes may be killed by chemotherapy, we examined the significance of the effect of treatment on the density of tumor-infiltrating lymphocytes and apoptosis in the tumor itself and in the tumor-infiltrating lymphocytes.', 'In 93 patients with esophageal cancer including 50 with neoadjuvant chemotherapy, esophagectomy specimens were examined for density of tumor-infiltrating lymphocytes and for apoptosis in both tumor cells and tumor-infiltrating lymphocytes.', 'Apoptotic index was increased by neoadjuvant chemotherapy only in tumor-infiltrating lymphocytes, apoptotic index was > or = 4 only in chemotherapy patients. The density of tumor infiltrating lymphocytes was a significant positive prognostic factor in chemotherapy and non-chemotherapy groups, and the high apoptotic index in tumor-infiltrating lymphocytes was an independent negative prognostic factor in the chemotherapy group.'] Does chemotherapy-induced apoptosis of lymphocytes in esophageal cancer worsen outcome?