The objectives of this study were: (1) to determine, using immunohistochemistry, the level of expression of the cell cycle factors p53, p21 and cyclin D1 in a group of bronchioloalveolar carcinomas (BACs), and to compare these data to relevant published data for lung carcinoma; (2) to determine if higher expression rates for these factors in BAC were associated statistically with advanced clinical stage, greater tumour size, tobacco abuse, and/or BAC subtype; (3) to seek, using Fisher's exact t-test and paired data groups, any significant associations within the expression data for p53, p21 and cyclin D1.Methods and results:
A panel of monoclonal antibodies against p53, p21 and cyclin D1 was applied to 19 bronchioloalveolar carcinomas (17 surgical pathology cases and two autopsies) from the tissue archives of St. Louis University. These immunohistochemical stains were graded on a semiquantitative scale according to the prevalence of nuclear staining within the tumour (<10% positive cells = 0, 10-25% = 1+, 25-50% = 2+, 50-75%= 3+ and 75-100% = 4+). Six of 19 (32%) of BACs showed 1+ or greater p53 positivity, six of 19 (32%) showed 1+ or greater nuclear cyclin D1 positivity, and nine of 19 (47%) of BACs showed 1+ or greater p21 nuclear positivity. A statistically significant correlation was found between p53 and cyclin D1 expression (P=0.046, Fisher's exact t-test), but not between p53 and p21, or between p21 and cyclin D1. No statistically significant association was found between the cell cycle factor expression data and subtype of BAC (mucinous vs. nonmucinous), tumour diameter, clinical stage or tobacco-use history.Conclusions:
BACs show p53 immunostain positivity at a frequency similar to that published for p53 mutations in lung adenocarcinomas in general. Cyclin D1 and p21 nuclear expression characterizes a significant proportion of BACs, with cyclin D1 and p53 expression showing a statistically significant association. Aberrations in p53, p21, and cyclin D1 expression may be important in the development of a significant proportion of BACs.