Breast Cancer Hormone Receptor Assay Results of Core Needle Biopsy and Modified Radical Mastectomy Specimens From the Same Patients

Background: Hormone receptor (HR) expression is the most important biomarker and is the cornerstone in the management of breast cancer. Therefore, the accuracy of its testing is critical in treatment decisions. Patients and Methods: A total of 160 consecutive patients accrued to an adjuvant hormonal therapy clinical trial between March 2003 and May 2008 were studied. Estrogen receptor (ER) and progesterone receptor (PgR) protein assays of tissues from modified radical mastectomy (MRM) specimens were compared with their previous core needle biopsy (CNB) ER and PgR immunohistochemical assay results. Results: The tumors of 146 (91.2%) out of the 160 patients with CNB HR-positive disease remained HR positive in MRM specimen assays. Estrogen receptor positivity decreased from 95% in the CNB to 81.9% in MRM specimens and PgR positivity from 93.8% to 86.9%. The overall agreement between CNB and MRM specimens was 81.9% for ER and 85.6% for PgR. The mean Allred scores were significantly higher in CNB than in MRM specimens: ER, 6.6 (SD, 2.02) versus 4.71 (SD, 2.62); PgR, 6.68 (SD, 2.16) versus 5.99 (SD, 2.68); P < .001 and P = .001, respectively. Conclusion: Core needle biopsy specimens are associated with the identification of more frequent and higher levels of tumoral hormonal receptor proteins than MRM specimens. Delayed fixation of MRM tissues likely accounted for this finding. Optimal selection of patients for hormonal therapies is dependent on tissue management strategies before formal hormonal receptor protein testing procedures.