Problems In Determining Her2 Status In Breast Carcinoma

Area of Science:

• Oncology
• Molecular Pathology
• Diagnostic Pathology

Background:

• Human epidermal growth factor receptor 2 (HER2) oncoprotein overexpression in 15-25% of breast carcinomas correlates with poor prognosis.
• Accurate HER2 status assessment is vital for patient selection for HER2-targeted therapies.

Purpose of the Study:

• To evaluate the accuracy of HER2 status determination using immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH).
• To identify challenges and reasons for discordant results in HER2 testing.

Main Methods:

• Utilized IHC and FISH to assess HER2 status in 308 breast carcinoma cases, including 129 consultation cases.
• Analyzed HER2 expression levels and gene amplification status.

Main Results:

• HER2 amplification detected in 28.6% of cases by FISH.
• Statistically significant correlation (p<0.001) between HER2 expression and amplification.
• High concordance rates: 95.4% for consultation cases, 100% for in-house cases, and 98.4% overall between IHC (+++) and FISH.

Conclusions:

• High concordance between IHC and FISH for HER2 status determination.
• Identified triple negativity, preanalytical, and analytical issues in consultation cases as potential reasons for discrepancies.
• Emphasized the reliability of combined IHC and FISH for accurate HER2 assessment in breast cancer.