Triple negative cancer

lymphoid tissue can be detected [14]. In contrast, increased numbers of lymphocytes are frequently detectable around and within breast cancers [15-18]. The clinical significance of TILs in breast cancer is still controversial. In some studies, TILs were associated with unfavorable characteristics such as high grade tumors, estrogen receptor negativity, basal-like molecular subtype as well as her2/neu positive tumors [19,20]. High CD4⁺ and CD8⁺ lymphocytic infiltration has been associated with positive lymph node status as well as worse overall survival [21]. Furthermore, in early stage breast cancer, CD8⁺ lymphocytic infiltration has been suggested to correlate with lymph node involvement [22]. Other groups, however, have shown that breast cancers with increased TIL number display a better prognosis in comparison with breast cancers with lesser lymphocyte infiltration [23], as also confirmed by data from our institution for CD8⁺ TILs in the ER negative subgroup [24]. Additionally, high TIL counts may represent an independent predictor of response to neo-adjuvant chemotherapy [25]. Notably, infiltration by FOXP3⁺ lymphocytes in breast cancer has been proposed to represent an independent unfavorable prognostic factor, especially in the nodal positive subgroup [26] and to correlate with tumor invasiveness [27]. In contrast, a complete clinical response has been suggested to be associated with disappearance of tumor infiltrating FOXP3⁺ T-cells during treatment [28].

While the clinical significance of TILs is controversial, their distribution within stromal and intratumoral compartments in breast cancers is largely unknown. Furthermore, T-cell infiltration in different histological subtypes as well as the occurrence of IL-17⁺ lymphocytes in breast cancer tissue has not been reported to date. Here, we addressed these issues by using a tissue microarray (TMA) including a large number (> 1000) of breast cancers stratified according to ductal and lobular histological subtypes. By taking advantage of a comprehensive clinical follow-up database, numbers of CD4⁺, FOXP3⁺ and IL-17⁺ TILs and their occurrence in different tumor compartments was correlated with clinico-pathological features and survival data.