Human cutaneous mast cells--a study of fixative and staining reactions in normal skin.

Routinely used formal saline fixation reduces the number of demonstrable mast cells in human skin by up to 30% compared with paired specimens fixed in Carnoys medium. Using metachromatic (toluidene blue), orthochromatic (alcian blue/safranin), enzymatic (chloroacetate esterase reaction) and immunofluorescence (berberine and fluorescein conjugated avidin) staining techniques, mast cells were demonstrated and quantified. Alcian blue/safranin and fluorescein-conjugated avidin were both superior to the other staining methods used. We recommend the use of Carnoys medium fixed tissue stained with either alcian blue/safranin or conjugated avidin for optimal visualization and assessment of mast cells in human skin.