Associations between BCL-2 expression and different histopathological prognostic factors in different molecular subtypes of invasive breast carcinoma of no special type

. Background. Breast cancer is heterogeneous and the existing prognostic classifiers are limited in accuracy, leading to the unnecessary treatment of numerous women. B-cell lymphoma 2 (BCL-2), an antiapoptotic protein, has been proposed as a marker of poor prognosis, associated with resistance to therapy in most tumor types expressing BCL-2. In breast cancer, however, BCL-2 expression has been reported to be a favorable prognostic factor. This study aimed to describe the association between BCL-2 and other well-known pathological prognostic markers among different molecular sub-types of invasive breast carcinoma of no special type (IBC; NST). Methods. BCL-2 expression, as well as that of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2), were immunohistochemically (IHC) evaluated and compared with other pathological factors, including tumor size, grade, tumor-infiltrating lymphocytes (TILs), lymph-vascular invasion (LVI), and lymph node (LNd) metastasis, in 128 breast cancer cases diagnosed with IBC; NST. Moreover, we analyzed the correlation between BCL-2 expression and relapse-free survival (RFS) in all patients over a two-year period. Results. We found that BCL-2 expression had different pathological prognostic factor associations with different molecular subtypes of breast carcinoma. In the luminal A (i.e., hormonal receptor-positive and HER2-negative) and triple-negative subtypes, the expression of BCL-2 in tumor cells was significantly associated with tumor size, tumor grade, and TILs. BCL2-positive expression in luminal IBC; NST patients resulted in a significantly favorable two-year survival. Conclusion. BCL-2 expression in IBC; NST has different prognostic effects depending on the molecular subtype of the cancer. In cancers with a HER2-enriched phenotype, BCL-2 expression was a marker of poor prognosis, while in cancers with a hormone receptor-positive phenotype, BCL-2 expression had a better prognostic impact.