Assessing HER-2 status in fresh frozen and archival cytological samples obtained by fine needle aspiration cytology

Determination of HER-2 status is an essential prerequisite in considering a patient's eligibility for anti-HER-2 therapy; few studies have focused on its evaluation on cytological material. We present a new method of assessing HER-2 status on cytological samples, by fluorescence in situ hybridization (FISH) with an automated detection system, using fresh frozen (FF) and May–Grünwald–Giemsa (MGG) stained smears, and we evaluate the reliability of HER-2 determination on fine needle aspiration cytology (FNAC). The pre-treatment protocol for FF smears is easier and faster than for MGG stained slides. However, with the described procedure, FISH is also feasible on archival MGG stained slides. We conclude that with this method, cytological samples obtained by FNAC, either FF or MGG, are a reliable option for assessing HER-2 status.