Analys av HER2 i bröstcancer kvalitetssäkrad. Viktig behandlingsprediktiv och prognostisk faktor.

Human epidermal growth factor receptor 2 (HER2) is overexpressed and/or
amplified in 15-20% of all breast cancers, and is associated with an aggressive tumour type
with impaired prognosis and a predictive marker for trastuzumab treatment. HER2 status can
be determined by immunohistochemistry (IHC) at protein level and by fluorescence in situ
hybridisation (FISH) analysing gene amplification, and it is recommended that it should be
performed in all primary breast cancers. In a quality control study the reproducibility of HER2 status was assessed by distributing eleven breast tumours prepared on a tissue microarray to 25 pathology laboratories in Sweden in 2005 and 2006. The concordance between the laboratories indicated good reproducibility for IHC 2005 (kappa value 0.79) and very good reproducibility for 2006 (kappa value 0.86). The corresponding reproducibility for FISH was very good on both occasions (kappa value 0.92 and 0.96 respectively). A questionnaire indicated that 90% of all primary breast cancers diagnosed in Sweden in 2006 were tested for HER2 status. By way of summary, HER2 status is now implemented in clinical routine diagnostics in Sweden, and the present reproducibility study supports a high quality of testing.