Fontana-Masson Stain for Melanin

At times it can be difficult to decide whether a brown pigment is lipofuscin, hemosiderin, or melanin. Usually the location is a key to identification, but journal editors are unreasonable creatures who eat their young and reject papers just for the fun of it; they always want more data before they'll accept a statement. In theory, if you were looking at a new species no one had ever examined before, it would be necessary to have some sort of proof of the assertion that it was one of the three. Luckily, hard working histologists and pathologists have developed methods that will allow you to convince even the most hard-bitten and cynical reviewer that you know what you have found.

The Fontana-Masson Stain is specific for melanin and "argentaffin granules" of the digestive tract, but most often used for the former. At pH4, melanin granules reduce silver nitrate to metallic silver, a histochemical reaction that reveals accumulations of black material wherever melanin is located. This is seen in the cytoplasm of skin keratinocytes in the image at left: it can also be used in other locations where melanin is found, such as in the nervous system.

| H&E | PAS | Masson's CT Stain | Verhoeff-van Gieson | Verhoeff-Masson | Mallory's CT Stain | Golgi Stain|

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