Trichrome

Trichrome refers to a class of histological staining methods that color three different tissue components with distinct colors, enabling the differentiation of cellular elements from connective tissue in a single section. The name derives from Greek tri- meaning three and chroma meaning color. Several widely used variants include Masson's trichrome, Mallory's trichrome, and Gomori's trichrome. While formulations differ, these stains typically employ three dyes applied in sequence, producing characteristic color patterns: connective tissue such as collagen stains blue or green, muscle fibers and cytoplasm stain red or pink, and cell nuclei stain dark.

Masson's trichrome is common in routine histology and highlights fibrous tissue for assessment of fibrosis and architectural features. Gomori's trichrome offers alternative color assignments that can emphasize different tissue components, and Mallory's trichrome is another historical variant used for similar purposes. The stains are particularly useful for distinguishing fibrotic changes from surrounding parenchyma and for evaluating tissue architecture in biopsies and research specimens.

Preparation and interpretation require careful fixation, timing, and pH control, as staining is sensitive to methodological variables. Overstaining or under-staining can obscure distinctions between tissue elements. Trichrome stains remain in routine use due to their simplicity, speed, and clear differentiation of collagen versus muscle and cytoplasm, though newer techniques and automated systems have expanded the available options.