The Tissue was a solitary nodule found on an elderly man's arm. It  looked
malignant. I don't think that it was endogenous biotin because the negative
controls were negative.  I also don't think that it was contamination in the
primary, because we did other tissues with that antibody and they all worked
out fine. We do antigen retrieval for TTF, but, we also do it for many other
ab's and they were all OK. Thanks Tom.

Tom Wells, BSc, ART
Supervisor, Immunohistochemistry Laboratory
Lions Gate Hospital
North Vancouver, BC
Canada