The prognostic impact of tumor-infiltrating lymphocytes (TILs) is intensively investigated in
breast cancer (BC). It is already known that
triple-negative breast cancer (TNBC), the most aggressive type of BC, has the highest percentage of TILs. In addition, there is an influence of
steroid hormone receptor expression (type I
nuclear receptors) on TIL subpopulations in
breast cancer tissue. The link between type II
nuclear receptors and the level of TILs is unclear. Therefore, the aim of this study was to quantify TILs in a panel of 264 sporadic breast
cancers and investigate the correlation of TIL levels with type I and II
nuclear receptors expression. TIL levels were significantly increased in the subgroup of TNBC. By contrast, they decreased in
estrogen (ER)- or
progesterone receptor (PR)-positive cases. Moreover, TIL levels were correlated with type II
nuclear receptors, including PPARĪ³, with a significant inverse correlation of the nuclear form (r = −0.727, p < 0.001) and a weak positive correlation of the cytoplasmic form (r = 0.202, p < 0.002). Surprisingly, BC cases with a TIL Salgado score of >15% showed a significantly decreased overall survival. In addition, peritumoral
inflammation was also quantified in BC tissue samples. In our cohort, although the level of peritumoral
inflammation was not correlated with OS, it determined the prognostic value of ER, PR, and PPARĪ³ in BC. Altogether, the present study provides a differentiated overview of the relations between
nuclear receptor expression, TIL levels, peritumoral
inflammation, and prognosis in BC.