Refinement of immunohistologic parameters for Her2/neu scoring validation by FISH and CISH

The conventional method of scoring Her2/neu immunostaining is recognized to result in a high false-positive rate among 2 + cases when compared with results obtained with fluorescence in situ hybridization (FISH); however, costs and convenience dictates that immunohistochemistry remains the screening test for Her2/neu status in patients with breast cancer. We describe refined criteria for scoring of Her2/neu on the basis of anatomic localization rather than the subjective assessment of intensity. The presence of a circumferential tram track pattern that results from the staining of apposing cell membranes in > 25% of the tumor cells was necessary for a 3 + score (Her2/ neu overexpressed) and the presence of the tram track pattern in < 25 % was scored 2 + (equivocal); granular and fragmented membrane staining was scored I + (negative). The tram track pattern of Her2/neu overexpression showed 100% concordance with gene amplification. FISH and CISH testing in selected cases from the other categories validated the revised scoring method. These criteria reduced the numbers of equivocal staining cases that required FISH testing.