The presence of amyloid maybe diagnostic (as in the case with lichen amyloidosis) or coincidental (as in basal cell carcinoma where its has no prognostic significance). Since the presence of amyloid is sometimes coincidental there is no need to do a special amyloid stain as it would not add any diagnostic value.
Amyloid can sometimes be easily recognised on a standard H+E stain as amorphous eosinophilic material, especially if it is ubiquitous in the sample. If only small amounts of ?amyloid are present (as may be in the case of lichen amyloidosis) this is where the amyloid special stain can come into play. Since the presence of amyloid can make or break the diagnosis the scientist needs to ensure his/her method and technique is up to scratch.
The Congo Red method, which requires light polarizing equipment, seems to remain the gold standard amongst most laboratories with the thioflavin method also popular. I have included below my favoured method for amyloid as is it very quick, only needs light microscopy and produces a very good visual result.
1. Sections to water
2. Stain with crystal violet solution (same as one used in Gram stain) for 2 – 3 mins.
3. Wash in water then diff in very weak (~0.2%) acetic acid for about 5 secs.
4. Wash in water and mount using aqueous mounting media
5. If wanted seal coverslip around the edges with nail varnish.
This is a metachromatic stain with the amyloid appearing pink/purple and the surrounding tissue staining purple.
I would invite anyone to submit their favoured amyloid staining technique along with its advantages and disadvantages.