Relationship between Molecular Subtype of Invasive Breast Carcinoma (IBC) and Expression of Gross Cystic Disease Fluid Protein 15 (GCDFP), Mammaglobin (MGB), and Androgen Receptor (AR)
GH Lewis, AP Subhawong, H Nassar, R Vang, J Hicks, A De Marzo, BH Park, P Argani. Johns Hopkins Medical Institutions, Baltimore, MD
Background: IBCs can be subtyped based on gene expression into Luminal (A and B), HER2 and basal-like carcinomas (BLCs). The relative frequency of expression of GCDFP, a marker of apocrine differentiation, has not to our knowledge been assessed in these subtypes. This is particularly relevant since recent studies suggest that the HER2 subtype overlaps with a molecular apocrine subtype which expresses AR and preferentially displays "apocrine morphology," though the latter seems somewhat subjective. In addition, MGB expression has rarely been analyzed in these IBC subtypes.
Design: Tissue microarrays (TMAs) were constructed from paraffin blocks of 71 IBCs and labeled by IHC for ER, PR, HER2, CK5/6 and EGFR to subtype them as Luminal A (ER+ and/or PR+; HER2-), Luminal B (ER+ and/or PR+; HER2+), HER2 (ER, PR-; HER2+), BLC (ER-, PR-, HER2-; CK5/6 and/or EGFR+), or Unclassified Triple Negative Carcinomas (UTNC) (ER, PR, HER2, CK5/6, EGFR-). Five 1mm diameter spots per case were taken. TMA sections were labeled by IHC for GCDFP, AR, and MGB. Any labeling with these markers was considered a positive result, and correlation with subtypes was analyzed.
|BLC||4.8% (1/21)||24% (5/21)||24% (5/21)|
|UTNC||0 (0/12)||17% (2/12)||17% (2/12)|
|Luminal A||65% (11/17)||80% (14/17)||82% (14/17)|
|Luminal B||71% (5/7)||85% (6/7)||71% (5/7)|
|HER2||71% (10/14)||71% (10/14)||71% (10/14)|