Immunohistochemical estrogen receptor assay: quantitation by image analysis

Area of Science:

• Oncology
• Pathology
• Biochemistry

Background:

• Estrogen receptor (ER) status is crucial for breast cancer treatment decisions.
• Biochemical dextran-coated charcoal (DCC) assay is a standard method for ER quantification.
• Immunohistochemical (IHC) assays offer potential advantages in tissue assessment.

Purpose of the Study:

• To compare the accuracy and reliability of an image-analyzed IHC ER assay with the biochemical DCC assay.
• To establish optimal cut-off points for IHC scoring using image analysis.
• To evaluate the utility of IHC ER assay quantitated by image analysis as an alternative to biochemical methods.

Main Methods:

• Comparison of ER quantification between biochemical DCC assay and image-analyzed IHC assay (ER-ICA) in 97 primary breast carcinomas.
• IHC staining utilized a monoclonal antibody and peroxidase-antiperoxidase technique.
• Image analysis quantified results using both semiquantitative microscopy (HSCORE) and quantitative nuclear area immunopositivity (PNA).

Main Results:

• Identical and significant correlation observed between DCC assay results and both HSCORE and PNA.
• Optimal cut-off points determined as HSCORE of 10 and PNA of 1% for sensitivity/specificity.
• High concordance between image-analyzed IHC results (HSCORE >150, PNA >15%) and high DCC results (>150 fmol/mg protein).

Conclusions:

• Image-analyzed IHC ER assay (PNA) is a comparable alternative to the biochemical DCC assay.
• This IHC method is particularly valuable when insufficient fresh tissue is available for biochemical testing.
• The study validates the use of quantitative image analysis for reliable ER status determination in breast cancer.