The trichrome stain is a favorite among pathologists. When well-applied, the stain results in a complex interplay of brilliant colors that offers not only beauty but diagnostic utility as well.

Created by French pathologist Claude L. Pierre Masson (1880-1959) in the early 20th century, the trichrome stain differentiates muscle and connective tissue cells in sharp relief, and is among the most frequently-used tools in a microscopist’s arsenal. The contrast between red muscle and keratin, blue or green connective tissue, pink cytoplasm, and black nuclei allows a skilled pathologist to evaluate liver, skin, kidney, and cardiac biopsies for increased fibrosis and to determine the relative proportions of smooth muscle and collagen in tumors. The application of the trichrome stain to post-mortem histology assists in identifying microscopic damage resulting from the poor blood flow and inadequate oxygenation associated with narrowing of the coronary arteries, as in this photomicrograph of an extensively scarred heart. Two forms of the trichrome stain are commonly used: a Masson trichrome stains connective tissue bright blue, while a Gömöri trichrome stain instead colors it green.