Concordance of immunohistochemistry in core needle biopsy and surgical specimen in invasive breast cancer

Introduction: Immunohistochemical (IHC) evaluation on core needle biopsy is essential to guide further treatment. The aim of our study was to determine the concordance of histology and IHC in CNB and SS in patients with invasive breast cancer (BC).

Material and methods: Retrospective analysis of data from patients with primary diagnosed BC at the university hospital of Berne between 2013 and 2015.

Results: A total of 84 patients with a mean age of 60.3 years (32 – 91) were eligible for this study.

Concordance analysis of receptor status revealed very good concordance for ER and PR expression; observed agreement 97.62% (k 0.896) and 94.05% (k 0.834), respectively. Less agreement was found for HER-2 receptor status (k 0.783). Agreement of Ki67 was very good (91.03%, k 0.817).

Regarding the molecular subtypes we found differences between CNB and SS in 15 (17.9%) patients. In 7 cases the tumor was reclassified from Luminal A in CNB to Luminal B in SS, in 5 cases from Luminal B to A, in one case from Luminal B to Her-2 positive, respectively from Her-2 positive to Luminal B and from triple negative to Luminal A. Comparing the subgroup of patients with a reclassification of molecular subtype in SS to those without, there was no difference in age, menopausal status, surgery and tumor size.

Conclusion: In 17.9% of the patients reassessment of IHC on the SS lead to a reclassification of molecular subtyp. Our study suggests that the immunohistochemical evaluation of the surgical specimen seems to be imperative.