The appropriate number of preoperative core needle biopsy specimens for analysis in breast cancer.

Ultrasound (US)-guided core needle biopsy (CNB) has been recognized as a crucial diagnostic tool for breast cancer. However, there is a lack of guidance for hospitals that are not equipped with adjunctive US. The aim of this study was to assess the sensitivity, specificity, and experience of freehanded CNB in the outpatient department, and to determine the minimum number of tissue strips required to obtain concordance for estrogen receptor (ER), progesterone receptor (PR), human epidermal growth factor receptor-2 (HER2), and tumor grade with the excised specimen.A prospective study was performed on 95 patients undergoing CNB and subsequent surgical procedures. The reliability of immunohistochemical assessments of the pathological type, tumor grade, ER, PR, and HER2 status in CNBs was compared with that of surgical specimens. Concordance between the CNBs and surgical samples was estimated as a percentage agreement, and analyzed using the chi-square test. A P < .05 was considered significant.The concordance rates of ER, PR, and HER2 status and tumor grade status between CNBs and surgically excised specimens were 97.9%, 91.6%, 82.1%, and 84.2%, respectively. The reliability of taking 2 tissue strips was similar to that of taking six tissue strips in distinguishing malignancy from benignancy, and determining the pathological type without the aid of US. Four tissue strips obtained by CNB showed good accuracy comparable to those obtained by surgical specimens in assessing ER, PR, and HER2 status and tumor grade.Two tissue strips obtained by CNB showed good accuracy in differentiating malignancy from benignancy, while at least 4 strips are recommended to obtain overall conformity of pathological biomarkers.