Pre-operative determination of oestrogen receptor status in breast cancer by immunocytochemical staining of fine needle aspirates.

The results of pre-operative staining of fine needle aspirate (FNA) samples from 48 breast cancers, with a polyclonal antibody raised against highly purified oestrogen receptor (ER) protein, have been compared with our standard biochemical method for measurement of cytosol and nuclear ER. FNA antibody staining correctly predicted the presence of ER in 20 of 21 ERC +/N+ tumours. There were 2 false positive results in 24 ER C-/N-tumours though both these tumours showed marked heterogeneity of staining. Three ER C+/N- tumours were negative by antibody staining, in keeping with the tendency for such tumours to be hormone independent in behaviour. This pre-operative method for ER determination appears to be a reliable alternative to other micro-assays for oestrogen receptors.