Discordance between core needle biopsy (CNB) and excisional biopsy (EB) for estrogen receptor (ER), progesterone receptor (PgR) and HER2 status in early breast cancer (EBC)

Patients and methods: Patients with EBC presenting to The Royal Marsden Hospital from June 2005 to September 2007 who had CNB and subsequent EB were included. ER and PgR were determined by immunohistochemistry (IHC) and graded from 0 to 8 (Allred score). HER2 was determined by IHC and scored from 0 to 3+. FISH analysis was carried out in HER2 2+ cases and in discordant cases. Results: In all, 336 pairs of samples were compared. ER was positive in 253 CNBs (75%) for 255 EBs (76%) and was discordant in six patients (1.8%). PgR was positive in 221 CNBs (66%) and 227 (67.6%) EBs being discordant in 52 cases (15%). HER2 was positive in 41 (12.4%) of the 331 CNBs in which it was determined compared with 44 (13.3%) EBs and discordant in four cases (1.2%). Conclusions: CNB can be used with confidence for ER and HER2 determination. For PgR, due to a substantial discordance between CNB and EB, results from CNB should be used with caution.