C-erbB-2 mRNA in breast cancer specimens that exhibit membrane or cytoplasmic immunoreactivity for c-erbB-2

Immunocytochemically detected membrane staining for c-erbB-2 in 20-30% of breast cancers correlates with a poorer prognosis for the patients. However, cytoplasmic immunoreactivity for c-erbB-2 has also been found in some specimens using some particular antisera, and it has been suggested that this staining arises from a protein located in the mitochondrial membrane. It is possible that this protein is an alternative form of c-erhB-2. In the present article, adjacent histological sections have been stained for c-erbB-2 immunocytochemically, and for c-erbB-2 mRNA by in situ hybridization. The results show the absence of c-erbB-2 mRNA in regions of cancer specimens that exhibit cytoplasmic staining for c-erbB-2, strongly suggesting that cytoplasmic staining for c-erbB-2 is an immunocytochemical artefact.