Prognostic Value of "Basal-like" Morphology, Tumor-Infiltrating Lymphocytes and Multi-MAGE-A Expression in Triple-Negative Breast Cancer

"Basal-like" (BL) morphology and the expression of cancer testis antigens (CTA) in breast cancer still have unclear prognostic significance. The aim of our research was to explore correlations of the morphological characteristics and tumor microenvironment in triple-negative breast carcinomas (TNBCs) with multi-MAGE-A CTA expression and to determine their prognostic significance. Clinical records of breast cancer patients who underwent surgery between January 2017 and December 2018 in four major Croatian clinical centers were analyzed. A total of 97 non-metastatic TNBCs with available tissue samples and treatment information were identified. Cancer tissue sections were additionally stained with programmed death-ligand 1 (PD-L1) Ventana (SP142) and multi-MAGE-A (mAb 57B). BL morphology was detected in 47 (49%) TNBCs and was associated with a higher Ki-67 proliferation index and histologic grade. Expression of multi-MAGE-A was observed in 77 (79%) TNBCs and was significantly associated with BL morphology. Lymphocyte-predominant breast cancer (LPBC) status was detected in 11 cases (11.3%) and significantly correlated with the Ki-67 proliferation index, increased number of intratumoral lymphocytes (itTIL), and PD-L1 expression. No impact of BL morphology, multi-MAGE-A expression, histologic type, or LPBC status on disease-free survival was observed. Our data suggest that tumor morphology could help identify patients with potential benefits from CTA-targeting immunotherapy.

Comparison of basal-like triple-negative breast cancer defined by morphology, immunohistochemistry and transcriptional profiles

Basal-like invasive breast cancer is an important clinical group because of its association with a triple-negative phenotype defined by the lack of expression of estrogen, progesterone and human epidermal growth factor receptors 2, relative lack of therapeutic options and poor prognosis. However, depending on the method used to define these lesions, morphological assessment, immunohistochemical markers or gene expression, a different set of tumors is captured. The aim of this study was to investigate the consequences of using different methodological approaches to define basal-like lesions among triple-negative breast carcinomas with regard to their clinicopathological features and patient outcome. The cohort consisted of 142 invasive breast cancers with a triple-negative receptor status. First, each was reviewed histologically and those with morphological basal-like features were characterized as 'Path-Basal'. Second, the 'Core Basal' immunohistochemical lesions, defined as cytokeratin 5/6 and/or epidermal growth factor receptor 1 positive, within the triple-negative breast cancers were identified, and third their classification based on gene expression profiling was retrieved and those in the molecular 'PAM50 basal-like' subtype recorded. A total of 116 basal-like breast cancers were identified among the 142 triple-negative breast cancers by at least one of these three classifications (80%), but only 13 samples were defined as basal-like with all three methods. None of these 13 tumors were associated with lymphovascular invasion. The 34 morphological 'Path-Basal' lesions were significantly associated with a lack of nodal metastases. Comparing the estimates of death in the three classifications, the highest risk of death was seen for the 'Core Basal' group. In this study, we highlight that the definition of basal-like breast cancer based on different methodologies varies significantly and does not identify the same lesions. This incomplete overlap of cases emphasizes the need for consistent or new approaches to improve precise identification.