Analysis of p53 from the patient's tumor. A) Elevated nuclear p53 expression in tumor cells is shown in this paraffin section by avidin-biotin complex immunohistochemistry. Control sections, which received non-immune serum, showed no immunoreactivity (data not illustrated). B) Automated fluorescent DNA sequencing analysis (antisense strand) demonstrated a missense mutation in exon 6 of p53. The upper and lower panels show the wild-type and tumor sequences respectively. The arrowhead shows the C→T mutation in the antisense strand.