Micropapillary lung adenocarcinoma: a distinctive histologic subtype with prognostic significance. Case series

The aims of the present work were to evaluate the prognostic significance of the micropapillary pattern of lung adenocarcinoma and determine whether there are differences in the behavior of this type of tumor according to its immunohistochemical profile. A series of 191 consecutively resected pulmonary adenocarcinomas were divided into those with (n = 62) and those without (n = 129) micropapillary components. The disease was stage I in 38 and 54 patients, respectively. The 5-year survival rates of patients with and without micropapillary components were 54% and 77%, respectively (log rank P = .03). In multivariate survival analysis, the micropapillary component proved to be an independent prognostic factor (hazard ratio, 3.2). Five autopsy cases were used to investigate the immunohistochemical profile. The percentages of cases positive for various markers were 56.7 for p53, 94 for Ki67, 85.1 for c-myc, 2.9 for Bcl-2, 35.8 for epidermal growth factor receptor, 43.3 for cyclin D1, and 46.3 for Bax. The prognostic value was evaluated according to the expression of the different markers in micropapillary carcinomas in stage I. In univariate analysis, only cyclin D1 expression and Bax expression were associated with significantly worse survival (log rank P = .03 and P = .02, respectively). We conclude that it is important to recognize the micropapillary growth pattern in lung adenocarcinoma. Moreover, cyclin D1 and Bax seem to be markers of a poor prognosis.