STUDY OF HER2/NEU STATUS OF LOCOREGIONALLY METASTASIZING BREAST CANCER CELLS IN THE CASES WITH EQUIVOCAL (2+) LEVEL OF HER2/NEU ONCOPROTEIN EXPRESSION IN PRIMARY TUMOR TISSUE
Purpose: to compare Her2/neu protein expression and Her2/neu statuses of primary breast cancer (BC) and its local metastases in cases with equivocal (2+) expression of this marker in primary tumor (PT). Material and methods. Her2/neu immunohistochemical study (Ventana) of PT and local metastases by 25 BC patients with equivocal (2+) Her2/neu expression in PT was performed. Her2/neu gene amplification in PT was evaluated by SISH (Ventana). ASCO/CAP guidelines were used. Her2/neu expression and statuses of PT and metastases were compared using Wilcoxon and Fisher exact probability tests, Cohen’s kappa was also used. Results. Of 25 studied cases in 80% Her2/neu expression in metastases was lower (0, 1+), in 4% higher (3+), in 16% the same (2+) if compared with PT. Her2/neu expression median was 1+ (IQR 1) in metastases, difference with PT was significant (p<0.001, Wilcoxon signed rank test). Frequency of cases with decreasing level of Her2/neu while metastasizing (80%) is significantly higher than frequency of cases with increasing of such level (4%) (p<0.05, Fisher exact probability test). Of 25 studied cases 20% had amplified Her2/neu gene in PT and in 4% metastasis had 3+ protein expression. Frequency of the same Her2/neu statuses of the primary tumor and metastasis was 84% (95% CI was 63.1-94.8%). Cohen’s kappa was 0.29 (fair agreement of positive and negative Her2/neu statuses of PT and metastasis).