Histopathological examination and analysis of estrogen (ER), progesterone (PR) and HER2 receptors expression in MpBC patients and their comparison to other types of invasive breast cancer has been performed.
PD-L1 expression was detected in a significantly higher proportion of MBCs (46%) than in other subtypes (6% each in hormone-positive and HER2-positive breast cancers, and 9% in TNBC, not otherwise specified, p<0.001).
All 16 MPBCs (100%) that were negative forERBB2 (HER2) overexpression by immunohistochemistry and/or ERBB2 (HER2) amplification by fluorescence in situ hybridization were also uniformly (100%) negative for ERBB2 amplification by next-generation sequencing-based copy-number assessment.