Fixation on Histology

There are several different classifications of silver stains a histologist can use in the lab. The silver stain classifications refer to the physicochemical reactions involved between the stain solutions and the tissue constituents. The four major categories are Argentaffin methods, Argyophilic methods, silver oxidation-reduction stains, and impregnation stains. For example, an Argentaffin stain, which is similar to a Fontana-Masson stain, can be used to identify melanomas and carcinoids because certain tissue elements, if present, can alter the ionic silver and change it to a metallic silver. The following chart outlines four silver stain classifications and the structures they are intended to identify.

Silver Stains are a very sensitive way of demonstrating micro-organisms.  The silver stain, when done well, doesn’t overstain the fungi and can allow for the visual clues needed to identify certain tissue constituents with the cells. Also, silver stains are more sensitive than PAS stains which do not stain non-viable organisms, only living organisms.  Lastly, the strong oxidizer, Chromic Acid, should inhibit other structures from staining with silver, which can irritate the pathologist.

There have been advances or modifications made to these stain classifications since their introduction, yet there remain challenges with some techniques or procedures involving silver. One advancement in impregnation stains—the use of decreased concentrations of silver solutions—has resulted in decreased costs and background staining. Another advancement has been the increased sensitivity of silver staining methods, particularly those used quantitatively. Some techniques, however, call for the use of a highly toxic carcinogen, pyridine. The lab may wish to investigate commercially prepared stain kits that do not use such hazardous chemicals. Another challenge with the impregnation technique is that controls may be difficult to obtain for some procedures.

Has your lab modified silver staining methods that yielded better results, cost savings, or improved diagnostic capabilities? Have the changes you employed better addressed some of the challenges associated with the different silver staining techniques? Let us and fellow members know in the comments section.     

You can learn more about Sliver Stain Classifications in the Webinar:  Theory and Application of Silver Stains in the Histology Laboratory presented by Debra Siena, HT(ASCP), QIHC