Hi Richard,
Although AE1/AE3 antibody, being a monoclonal cocktail, is supposed to
be fairly wide spectrum and stain both squamous and simple epithelium,
my experience is that it misses some squamous eptihelium (maybe due to
formalin fixation). I never use it alone, particularly when doing a skin
lesion, but also run a wide spectrum polyclonal keratin antibody (Dako).
Over the years I've done immuno, I've come accross a few squamous cell
carcinomas totally negative for AE1/AE3, but nicely positive with the
other.
Katri

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