The identification of myoepithelial cells in human salivary glands. A review and comparison of light microscopical methods.

Myoepithelial cells have frequently been implicated in salivary gland tumour histogenesis. A major problem has been the reliable identification of these cells at the light microscopical level, both in tumours and in normal salivary glands. Many methods have been advocated, often with comparatively little evaluation in normal human tissue and with limited comparison between techniques. This paper reviews the application of histological staining techniques, enzyme histochemistry and immunocytochemistry with antibodies to actin, myosin and keratins. The only reliable method was immunocytochemistry with an antibody to smooth muscle myosin, with immunofluorescence on frozen tissue and immunoenzyme labelling on methacarn-fixed/paraffin-processed material. Formalin fixation did not permit successful staining. Monoclonal antibodies to specific keratin polypeptides may prove to be a useful label of myoepithelial cells but at the present time the available cytokeratin antibodies preferentially stain duct cell populations.