CD8(-CELLS INFILTRATED WITHIN CANCER CELL NESTS AS A PROGNOSTIC FACTOR IN HUMAN COLORECTAL-CANCER() T)

The pathophysiological significance of tumor infiltrating lymphocytes remains controversial, To clarify their role, we performed clinicopath ological analysis of CD8(+) T cells in 131 cases of human colorectal c ancer. CD8(+) T cells were classified into three groups by their local ization: (a) those infiltrated within cancer cell nests; (b) those dis tributed in the cancer stroma; and (c) those present along the invasiv e margin (tumor-host interface). Of these, CD8(+) T cells within cance r cell nests were most significantly associated with a better survival of patients by both mono-and multivariate analyses. The impact on sur vival was similar to that of Dukes' staging. Granzyme B+ cytoplasmic g ranules were detected in lymphocytes within cancer cell nests, confirm ing their activated, cytotoxic phenotype. CD8 and Ki-67 double immunoh istochemistry confirmed higher proliferative activity of CD8(+) T cell s within cancer cell nests. Our data suggested that human colorectal c ancer tissue was infiltrated by various numbers of T cells that had cy totoxic phenotype, contributing to a better survival of patients. This infiltration of colorectal cancer cell nests by CD8(+) T cells could be a novel prognostic factor.