Evaluating histopathological features in different biological breast cancer groups before and after neoadjuvant chemotherapy

Background Neoadjuvant chemotherapy (NACT) refers to the systemic treatment of Breast cancer (BC) before definitive surgical therapy to downstage the tumor, facilitate less extensive surgery on the breast and/or axilla, and reduce postoperative complications such as lymphedema. Clinico-pathologic features such as age, radiological tumor size, focality, histologic type, grade, Duct carcinoma in situ (DCIS), tumor-infiltrating lymphocytes (TILs), and the biological subtypes of the tumor based on the pre-NACT core needle biopsy evaluation play a crucial role in predicting the response to NACT. Aim To assess histopathological parameters before and after NACT and their potential predictive value for NACT response in different biological BC subtypes. Patients and methods This study covered a total of 99 cases who received NACT. Revision of H&E slides, along with immunohistochemically stained slides of pre-NACT core biopsy of these cases were applied to confirm the diagnosis, classify BC into different biologic subtypes as per the established surrogate markers, and record relevant prognostic histopathological findings. Tumor histologic subtype, grade, DCIS, and TILs were evaluated. Post-NACT specimens’ H&E slides were also examined to assess and determine NACT response. Results Pathological complete response (pCR) was achieved in 17.17% of the studied cases. Achieving pCR was statistically significant related to the absence of pre-NACT DCIS ( P 0.01), higher values of continuous and categorical TILs ( P 0.002 and 0.01, respectively), human epidermal growth factor receptor 2 (Her2) positive expression ( P <0.001), and high Ki67 greater than or equal to 20% ( P 0.05). Most pCR cases corresponded to the luminal B (HR+/Her2+) subtype, followed by Her2-enriched subtype. Moreover, pCR showed no significant relation to the age of disease onset, pre-NACT tumor size, pre-NACT histologic type, or grade. Conclusion This study suggests that pre-NACT TILs and Ki67 could be potential strong predictors of NACT response, thus emphasizing their vital role in BC cases.