Prognostic significance of CD8+ T lymphocytes in breast cancer depends upon both oestrogen receptor status and histological grade

Aims: Results of previous studies on the influence of tumour infiltrating lymphocytes on prognosis of women with breast cancer have been mixed. This study reevaluates the role of tumour-infiltrating lymphocytes as a prognostic marker in women with breast cancer. Methods and results: Immunochemistry staining of CD8(+) T cells was performed on a tissue microarray of 1953 breast carcinomas. When all tumours were considered, no association between the lymphocyte count and patient survival was found. In univariate analysis, there was a reduced disease-specific survival for women with oestrogen receptor (ER)-positive tumours with high intraepithelial lymphocyte count (P = 0.004). In those with ER-negative tumours, the disease-specific survival was improved when the intraepithelial, stromal and total lymphocyte counts were high, the total lymphocyte count also being an independent prognostic marker on multivariate analysis (P = 0.031). When stratified by histological grade, on univariate analysis, the previously observed inferior outcome in women with high lymphocyte count and ER-positive tumours remained significant only if tumours were also of low grade, and the superior outcome in those with ER-negative tumours remained significant if tumours were also of high grade. Conclusions: Our results raise the possibility of different immune-tumour interactions based on ER status and histological grade.