The analysis of 535 patients, in which both variables were available (Supplementary Table 1), showed a median tumor stromal lymphocytic infiltration of 5% (Q1-Q3: 4–15), with significant differences between immunohistochemical surrogate BC molecular subtypes (p < 0.001): higher values of sTIL were found in triple negative breast cancer (median 10%, Q1-Q3: 5–36) and in HR-/HER2 + tumors (median 20%, Q1-Q3: 5–30), while luminal BC cases showed lower infiltration (median 5%, Q1-Q3: 0–10). Here, ERBB2 is linked to triple-negative breast carcinoma.