Figure 1

Immunohistochemical staining for maspin (A, B, E, F) and for myosin heavy chain (C, D) in two breast tumours, one with normal maspin expression (A, C, E) and one with maspin overexpression (B, D, F). Intense maspin immunoreactivity was found in tumour epithelial cells from the maspin mRNA-overexpressing tumour (B) but not in cells (star) from the tumour without maspin overexpression (A) (original magnification × 20). Note the negative myosin heavy-chain staining of tumour epithelial cells from the maspin mRNA-overexpressing tumour (D), confirming that the latter is not of myoepithelial origin (original magnification × 20). In both cases, normal breast tissue showed maspin immunoreactivity in normal myoepithelial cells (arrows) (A, B), which also showed strong immunoreactivity for myosin heavy chain (C, D) (original magnification × 20). Maspin immunoreactivity was localised in the cytoplasmic compartment of both epithelial tumour cells (F) and normal myoepithelial cells (E) (original magnification × 100).