Mucinous differentiation in colonic adenocarcinoma is associated with a reduction in tumour-infiltrating lymphocytes

Aims: The aim of this study was to examine the density of tumour infiltrati ng lymphocytes (TILs) in colorectal carcinomas showing mucinous differentia tion. Methods: We examined 33 adenocarcinomas showing variable mucinous different iation and compared the density of TILs with that of 65 adenocarcinomas of no special type (NOS) showing no mucinous differentiation. Results: Mucinous differentiation is associated with a significantly lower density of TILs compared to adenocarcinoma NOS (P = 0.0016; chi-squared tes t with continuity correction). This reduction in TILs is present also in ad jacent foci of adenocarcinoma NOS within mucinous tumours. Conclusions: There is a reduction in the number of TILs in all areas of col orectal adenocarcinomas that show mucinous differentiation, which may help explain the increased biological aggressiveness associated with this patter n of differentiation. (C) 2001 Harcourt Publishers Ltd.