Cytoplasmic staining of c-erbB-2 is not associated with the presence of detectable c-erbB-2 mRNA in breast cancer specimens.

The cell-surface receptor tyrosine kinase protein c-erbB-2 is immunocytochemically detected as membrane staining on the surface of cancer cells in 20-30% of cases of breast cancer, and its presence has been associated with poor prognosis for the patient. However, there have been numerous reports of immunocytochemical staining for c-erbB-2 solely in the cytoplasm of some normal and tumour specimens with frequently used anti-sera, and the presence of such staining has been difficult to interpret. It is not known for certain that cytoplasmic c-erbB-2 staining is an artefact of the immunocytochemical procedures used. Thus, mRNA for c-erbB-2 has been quantified in tumours exhibiting only cytoplasmic staining or varying levels of membrane staining using a sensitive, competitive PCR method. Whereas abundant levels of c-erbB-2 mRNA are found in tumours exhibiting membrane staining for c-erbB-2 and these levels correlate with the percentage of tumour cells showing membranous staining for c-erbB-2, the level of c-erbB-2 mRNA in tumours displaying only cytoplasmic staining is no higher than in c-erbB-2-negative specimens.