Fontana-Masson
Author: Kelsey Goldman, HTL (ASCP)
Last Update: 11 July 2023
Copyright: 2023, HistologyOutlines.com
Cite this Page! -> Goldman, Kelsey. “Fontana-Masson.” HistologyOutlines.Com, 11 July 2023. Accessed (today)
Special Stain
Purpose:
- The Fontana Masson Stain is used to idenifty silver reducing Agrentaffin molecules in a tissue section. These Agrentaffin molecules inclue those of melanin, some kinds of fungi, and chromaffin (West et al.) (Method of the Histochemical Stains and Diagnostic Application – Department of Pathology and Laboratory Medicine – University of Rochester Medical Center)
- Any known tissue sample containing melanin. Example- pigmented skin. Ensure that the skin contains just enough pigment to stain, butu not so much that the presence of staining can not be verified
- Argentaffin cell granules, chromaffin, melanin and other substances that reduce silver- black
- All other parts of the tissue are pink because of counterstaining with Nuclear Fast Red (Method of the Histochemical Stains and Diagnostic Application – Department of Pathology and Laboratory Medicine – University of Rochester Medical Center).
- Fontana Masson Staining is a silver stain that relys on the tissue pricipal of Agrentaffin molecules in order to fuction. Agrentaffin molcules are those molecules that are found in tissue that can themselves reduce silver to the visable metalic form ( as opposed to the technican having to add a chemical to induce this reduction). In the case of Fontana Masson staining. The most important molecule that has Aggrentaffin properties is Melainin. In Fontana Masson Staining Ammonical silver is applied (heated or room temperture according to protocal). The silver in this soltuon is reduced to visable silver. The sections are washed then treated with Sodium Thiosulfate to remove any access silver that may still be present on the slide. The sections are then washed again and counterstained in Nuclear Fast Red There is debate regarding of Fonatana Masson is the best stain to use for the detection of melanin. Some pathologist agruge that Warthin Stary is a better method, as some studies show that Warthin Starry is more sensative (Joly-Tonetti et al.).
- In Fontan Masson staining it is critical to observe what glasswear and forcepts are used. Improperly cleaned and dirty glasswear will cause residue to interact with the Fontana Masson Reagents. This interaction may lead to nonspecific or under staining. Also, the use of metal forceps must be avoided ( plastic forceps are fine). The Ammoniacal Silver will react with the metal causing poor staining (Suvarna et al.)
- Sections in which the tissue was fixed with chromate or mercury chloride based fixatives should be avoided for Fontana Masson Staining (Suvarna et al.)
- Protocols for Fontana Masson Staining will vary. It is not uncommon to encounter a protocol that includes heating the ammoniacal silver in an oven for a prolonged time. While this can lead to superior staining, it also causes a black precipitate to form on the surface of the fluid. This precipitate must be filtered out before the slides are placed into the solution. If not, the precipitate will stick to the slide creating an unacceptable “flaky” artifact (Suvarna et al.).
- It is important not to over incubate the sections in ammoniacal silver, particularly of using a heated solution. This will lead to over staining and overall poor quality (Suvarna et al.).
- There exists a controversial artifact in Fontana Masson Staining called “melanin dust”. This artifact is composed of small dust like particles in the topmost layer (stratum Corium) of the skin. It is unclear as to why this occurs (Joly-Tonetti et al.).
- Joly-Tonetti, Nicolas, et al. “Melanin Fate in the Human Epidermis: A Reassessment of How Best to Detect and Analyze Histologically.” Experimental Dermatology, vol. 25, no. 7, 2016, pp. 501–04, https://doi.org/10.1111/exd.13016.
- Kiyohara, Takahiro, et al. “Site‐specific Acral Nevus Histologically Reminiscent of Melanoma: Recognition of the Utility of the Fontana–Masson Stain.” The Journal of Dermatology, vol. 46, no. 5, 2019, pp. e183–85, https://doi.org/10.1111/1346-8138.14735.
- Method of the Histochemical Stains and Diagnostic Application – Department of Pathology and Laboratory Medicine – University of Rochester Medical Center. https://www.urmc.rochester.edu/urmc-labs/pathology/stainsmanual/index.html?MICROWAVEAMMONIACALSILVERMETHODFORARGENTAFFINANDMELANIN. Accessed 7 Sept. 2023.
- .Suvarna, S. Kim, et al., editors. Bancroft’s Theory and Practice of Histological Techniques. Eighth edition, Elsevier, 2019.
- West, Kelly Leigh, et al. “Fontana-Masson Stain in Fungal Infections.” Journal of the American Academy of Dermatology, vol. 77, no. 6, 2017, pp. 1119–25, https://doi.org/10.1016/j.jaad.2017.02.052.