Dear Liz,
If you let me have your fax number I will let you have a copy of a 
paper I recently had published on false positives and false 
"specificity" with p53 (and other proliferation markers) in oral 
carcinomas.

The reference is:  Allison RT & Best T. p53, PCNA and Ki-67 
expression in oral squamous cell carcinomas: the vagaries of fixation 
and microwave enhancement of immunocytochemistry.
J Oral Medicine & Pathology 1998:27;434-440.

We use a colonic carcinoma as our (positive) control
Russ Allison, Wales