Masson’s Trichrome staining for histology v1

Masson's trichrome is a histological staining method commonly used to distinguish collagen from muscle, cytoplasm and other tissue components. The method presented here remains close to the original used by Masson in 1929. While there are many variants of the original method, there is commonality in that they all utilise three components - a nuclear stain (usually an iron haematoxylin), a fibre stain (to specifically dye the collagen) and a plasma stain (which acts as a counterstain). They also consistently use a polyacid to differentiate the plasma staining. In this method it is noted that, if using routine formalin-fixed paraffin-embedded tissues, including the optional mordanting step will increase staining intensity and enhance contrast between tissue components. The same effect can also be achieved by using Bouin's fixative. Nuclear stain: This method uses Weigert's haematoxylin as the nuclear stain by staining the nuclei dark purple-black. Some variants use Verhoeff's haematoxylin to additionally highlight elastin by staining it black. Plasma stain: This method uses the original red dyes for the plasma stain, specifically a mixture of Acid fuchsin and Ponceau de xylidene. The latter has a number of alternate names, including Xylidine Ponceau, Xylidine Ponceau 2R, Ponceau 2R, Ponceau G, Ponceau Red, Acid Red 26. All have the same C.I. 16150. Common variants use a mixture of Acid fuchsin and Biebrich scarlet, which provides a similar result, with a slightly darker red. Heteropolyacid: Like the original, this method uses a 1% phosphomolybdic acid (PMA) solution for the heteropolyacid. Most variants use the same, but some recommend combining with phosphotungstic acid (PTA) in a 2.5% PMA + 2.5% PTA solution. Fibre stain: The fibre stain used here is Methyl blue which stains collagen a vibrant, royal blue. This is similar to the orginal Masson's method, which was thought to use Aniline blue water soluble (a mixture of Water blue and Methyl blue). Some other variants use green fibre stains, such as Light green or Fast Green FCF. The Fast Green FCF resists fading better than Light green, which fades over time, causing sections to lose their contrast. One uncommon variant uses Metanil yellow to stain the collagen yellow.