Nuclear p53 immunoreactivity in papillary thyroid cancers is associated with two established indicators of poor prognosis.

The tumor suppressor protein, p53, protects somatic cells against the accumulation of genomic alterations. Cells harboring mutant or inactivated wild-type p53 protein are at risk for the development of genomic instability. Nuclear accumulation of p53 protein is associated with the stepwise dedifferentiation of papillary carcinoma. We asked whether nuclear p53 accumulation is associated with two known indicators of poor prognosis in papillary carcinoma. We studied 55 consecutive papillary cancers (28 from Russia, and 27 from upstate New York). Nuclear p53 immunoreactivity was assessed using a monoclonal antibody, DO-1, on Formalin-fixed paraffin-embedded specimens. The DNA index was determined by computerized image analysis of Feulgen-stained sections. Nearly all cases were well differentiated and none were associated with distant metastases or extrathyroidal invasion. All primary lesions were less than 4 cm in diameter, and almost all patients were female. Nuclear p53 immunoreactivity was associated with a high-risk group characterized by two known indicators of poor prognosis: age > 50, aneuploid DNA content, or both. In the high-risk group (N = 24) 33% of cases displayed nuclear p53 positivity, compared with only 6% in a low-risk group (N = 31) which lacked both features (P = 0.015, two-tailed Fisher exact test). Nuclear accumulation of immunoreactive p53 protein is associated with two established indicators of poor prognosis in papillary carcinoma of the thyroid. This result is consistent with the idea that aberrations in p53 function are associated with the stepwise loss of differentiation in this cancer.