Abstract
Carbonic anhydrase III, a major protein of red skeletal muscle, was localized immunohistochemically in smooth muscle cells of human uterus and in myoepithelial cells of mammary and prostate glands. The presence of this antigen in myoepithelial cells could be used to detect these not easily recognizable cells in paraffin-embedded tissue sections. Some epithelial cells of larger mammary ducts revealed occasional strongly positive cells. These cells may represent a new epithelial cell type transitional between myoepithelium and ductal epithelium.