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 anti-apoptotic 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.