Tumor-infiltrating lymphocytes (TILs) have a strong prognostic and predictive significance, particularly in triple-negative breast cancer (TNBC). One important source of TILs in breast cancer is tertiary lymphoid structures (TLSs). Here, we performed histologic analysis of surgically resected TNBC to identify the location of TLSs, the relationship between TLSs and TILs, and their prognostic significance in TNBC. We retrospectively analyzed 769 patients with TNBC. TILs were defined as the percentage of stroma of invasive carcinoma infiltrated by lymphocytes. TLSs were mainly present within adjacent terminal duct lobular units and around in situ components. TNBC with higher levels of TILs showed a higher nuclear grade, lower lymphovascular invasion rate, less accompanying in situ component, a homogeneous growth pattern, necrosis in invasive areas, low levels of tumor stroma, high levels of peritumoral lymphocytic infiltration, and moderate to abundant TLSs in adjacent tissue. TILs, degree of peritumoral lymphocytic infiltration, and adjacent TLSs were prognostic factors for disease-free and overall survival outcomes. Although the TIL level did not have a prognostic value in stage I, it added significant prognostic information for stages II and III. Conversely, patients with high levels of TILs did not show prognostic differences according to the pTNM stage. Patients with high levels of TILs (>60%) and moderate to abundant TLSs had significantly better disease-free survival outcomes than those with high levels of TILs but none or few TLSs. TLSs are frequently present in TNBC and are closely associated with TILs. TILs provide additional prognostic information in TNBC patients with a higher pTNM stage.

Citation Format: In Ah Park, Hee Jin Lee, In Hye Song, Joo Young Kim, Jong Han Yu, Gyungyub Gong. Tertiary lymphoid structures: Prognostic significance and relationship with tumor-infiltrating lymphocytes in triple-negative breast cancer. [abstract]. In: Proceedings of the CRI-CIMT-EATI-AACR Inaugural International Cancer Immunotherapy Conference: Translating Science into Survival; September 16-19, 2015; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2016;4(1 Suppl):Abstract nr A163.