Histological grading of breast cancer on needle core biopsy: the role of immunohistochemical assessment of proliferation

Histological grading of breast cancer on needle core biopsy: the role of immunohistochemical assessment of proliferation Aims: Histological grade assessed on needle core biopsy (NCB) moderately concurs with the grade in the surgical excision specimen (SES) (kappa-values between 0.35 and 0.65). A major cause of the discrepancy is underestimation of mitoses in the NCB specimen. The aim was to determine the best method of assessing proliferation on NCB. Methods and results: Proliferative activity of 101 invasive carcinomas of the breast on NCB and SES was assessed using mitotic counts on routine haematoxylin and eosin (H&E) sections and immunohistochemical markers Mib-1 and phosphorylated histone H3 (PPH3). H&E mitotic count in SES was considered as the gold standard. H&E mitotic count was found to be underestimated on NCB when compared with that in SES (P < 0.001), but no significant difference was detected between NCB and SES regarding Mib-1 (P = 0.13) or PPH3 (P = 0.073). Using receiver-operating characteristic curve, Mib-1 on NCB was found to agree with the gold standard significantly better than routine H&E on NCB. Conclusions: Immunohistochemical markers in NCB showed better concordance with H&E mitotic count in SES (gold standard) than routine H&E mitotic count in NCB. Further refinement of cut-offs and scoring methods is needed.