--Method: 5 microM formalin-fixed paraffin-embedded sections are deparaffinized and blocked with methanol-30% hydrogen peroxide (H2O2). After antigen retrieval by boiling in citrate buffer, or heating in a microwave oven for 10 minutes, slides are incubated with monoclonal antibodies anti-CEA (diluted 1/1000 Dako). Then, slides are immunostained with avidin-biotin-peroxidase complex and developed with diaminobenzidine. Harris' hematoxylin was used to counter stain the slides. Positivity is defined as greater than 30% of cells staining.