POTENTIAL UTILITY OF P53 IMMUNOPOSITIVITY IN DIFFERENTIATION OF ADENOCARCINOMAS FROM REACTIVE EPITHELIAL ATYPIAS OF THE LUNG

Reactive atypia of alveolar epithelium occurs in many types of lung in jury and may sometimes raise suspicions of adenocarcinoma or bronchiol oalveolar carcinoma. To assess whether there is sufficient difference in the frequency of p53 protein immunopositivity in these lesions to p rovide a practical basis for differentiating malignancy from reactive atypia, we immunostained 110 malignant and inflammatory/fibrotic lung specimens for p53 protein. Paraffin-embedded sections were immunostain ed with p53 protein antibody (clone BP53-12; BioGenex, San Ramon, CA) and standard capillary gap (Microprobe; Fisher Scientific, Fairlawn, N J) avidin- biotin complex technique with antigen retrieval solution. P ercent of immunopositive cells was semiquantitatively categorized as f ollows: 0%, less than 1%, 1% to 10%, 10% to 50%, more than 50%, Of rea ctive atypias, 94% are negative or show p53 immunopositivity in less t han 10% of cells. Of p53 positive malignancies, 86% are positive in mo re than 10% of cells. When p53 immunopositivity occurs in more than 10 % of atypical cells, the lesion is usually a malignancy, primarily ade nocarcinoma. Most reactive atypias are immunopositive in less than 10% of atypical cells. Important caveats were noted. Rare reactive atypia s are p53 immunopositive in greater than 10% of cells. Bronchioloalveo lar carcinomas are infrequently p53 immunopositive. Therefore, this ap proach would be less useful in their differentiation from reactive aty pias. Copyright (C) 1996 by W.B. Saunders Company