Comparative Pathologic Analysis of Breast Cancers Classified as HER2/neu-Amplified by FISH Using a Standard HER2/CEP17 Dual Probe and an Alternative Chromosome 17 Control Probe

This study examines whether cancers that are classified as HER2-amplified with an alternate probe are clinicopathologically similar to those that are classified as such using the HER2/CEP17 probe. Reports for 1201 breast cancers were reviewed, and clinicopathologic findings were compared between HER2/CEP17-equivocal cases that became HER2-amplified using the alternate probe (group A: n=48), HER2-amplified cases using the HER2/CEP17 probe (group B: n=169), and HER2-nonamplified cases using the HER2/CEP17 probe (group C: n=910). Of 1201 cases tested using the HER2/CEP17 probe, 169 (14%) were HER2-amplified, 122 (10%) were equivocal, and 910 (76%) were nonamplified. Additional testing with the alternative probe on the 122 equivocal cases reclassified 48 (39%) of them to HER2-amplified, and such cases comprised 22% of all HER2-amplified tumors. A higher proportion of tumors with HER2 copy number between 5.0 and 5.9 became positive upon additional testing when compared with those with a priori HER2 copy numbers between 4.0 and 4.9 (P=0.0362). Group A cases, compared with group B cases, were more frequently positive for estrogen receptor (97.91% vs. 72.18%, P
Source: The American Journal of Surgical Pathology - Category: Pathology Tags: Original Articles Source Type: research