Determination of HER-2 status on FNAC material from breast carcinomas using in situ hybridization with dual chromogen visualization with silver enhancement (dual SISH)

Abstract

During the last years, HER-2 status kits and protocols for chromogen visualization of hybridization signals have come on the market. The first generation using chromogen visualization used single color probes. The second generation, now emerging on the market, uses dual chromogen visualization. The aim of this study has been to test a new dual color chromogen kit (Ventana INFORM HER2 Dual Colour ISH Roche(®)) and compare the results with our in-house method(s). The material consisted primarily of cytological material from invasive breast carcinomas in 49 women. Dual SISH was done on all 49 cytological and histological specimens. The histological specimens were treated according to the manufacturer's recommendations. The procedure was modified in several steps in order to adapt it to the cytological material. Hybridization failed in two cytological specimens. Dual SISH showed concordant results on cytological and histological material as to amplified/not amplified. The included cases had the same HER-2 expression in the invasive and the in situ components on histology. Four IDC showed HER-2 amplification (8.5%). Polysomy was found in two cases. All dual SISH results except for one concurred with the results of the in-house method(s) (1/47=2.1%). The dual SISH is suitable for cytological examination of HER-2 status. The protocol must be optimized for cytological material.

Keywords: Breast carcinoma; HER-2; dual SISH; fine needle aspiration cytology; in situ hybridization; liquid based material.

Figure 1a

Dual color SISH. Magnification × 1000. Cytological specimen, direct smear. Non-amplified with two signals of CEP17 (red) and HER-2 gene (black) per nucleus

Figure 1b

Dual color SISH. Magnification × 1000. Histological specimen. Non-amplified with two signals of CEP17 (red) and HER-2 gene (black) per nucleus

Figure 2a

Dual color SISH. Magnification × 1000. Cytological specimen, liquid based preparation. Two CEP17 (red) signals and from 5 to > 10 HER-2 gene signals (black) per nucleus. Amplification.

Figure 2b

Dual color SISH. Magnification × 1000. Histological specimen. Two CEP17 (red) signals and a highly increased number of HER-2 gene signals (black) per nucleus. Amplification.

Figure 3

Dual color SISH. Magnification × 1000. Cytological specimen. Liquid based preparation. Polysomy with increased number of both CEP17 (red) and HER-2 gene (black) per nucleus