TILs are classified as stromal or intratumoral and are graded visually on H&E sections using a continuous scale.4 The degree and type of lymphocytic infiltrate is prognostic in the neoadjuvant,6 adjuvant7 and metastatic8 settings for triple-negative breast cancer (TNBC) and HER2+ breast cancer as well as predictive of a higher likelihood of a pathologic complete response (pCR) with neoadjuvant chemotherapy.9 The gene discussed is ERBB2; the disease is breast carcinoma.