[Histonet] fontana masson

[Pereira, Laurie]

Hey everyone,

Let me start by saying this is my first time doing a Fontana Masson stain.  The pathologist was looking for a melanoma but decided later that it might be a venereal disease in a dog.  We make up our own solutions in the laboratory and our ammonium hydroxide is old.  It took at least 20ml to get the solution to change initially!  With that to say, my control and tissue sample have this non-specific brown pigment in the background.  It is not just in the cytoplasm of the cells.  It even occurs in the emtpy space of a hair follicle and exists in the background where tissue doesn't exist.  My control is a skin control and the melanin stained beautifully black.  What is this pigment?  I hope someone can help!  Thanks in advance!

Laurie L. Pereira, RVT
SDCADDL (County Veterinarian)
5555 Overland Avenue Suite 4103
San Diego, CA. 92123
Phone: 858-694-3384
Fax: 858-571-4268