Hi Mike,

The potassium permanganate bleach will destroy the antigenicity. I use
AEC instead of DAB as the chromogen for those cases with any endogenous
brown pigment.
AEC produces a red end product, which is easily distinguishable from the
melanin pigment. You'll just have to use an aqueous mounting media.

Katri

Katri Tuomala
Anatomic Pathology
St.Joseph's Hospital
Hamilton, Ontario, Canada