This study attempts to evaluate the clinicopathologic features of mixed subtype adenocarcinomas and the prognostic implications of histopathology classifications. Surgical specimens from 141 patients with clinical stage I or II lung adenocarcinoma during the period 1992-2004 were included. These cases were classified into four groups defined by the extent of the bronchioloalveolar carcinoma component: group I: pure bronchioloalveolar carcinoma; group II: mixed subtype with predominant bronchioloalveolar carcinoma component and < or = 5 mm invasive component; group III: mixed subtype with bronchioloalveolar carcinoma component and > 5 mm invasive component; group IV: invasive carcinoma with no bronchioloalveolar carcinoma component. Descriptive statistics were used to examine the groups with respect to age, tumor size, lymph node metastasis, and Ki-67 and p53 expression levels. Death rate for the groups was obtained by patient's charts and from the National Death Index database. The population was similar in age, tumor size and lymph node metastasis. Immunohistochemical results showed that the mean Ki-67 labeling and the amount of p53 overexpression had the same trend of increasing mean values or positive results from groups I to IV. The reported proportion of deaths ranged from 0% for groups I and II, 20% in patients with predominant invasive component with bronchioloalveolar carcinoma (group III), and 18% in patients with invasive carcinomas and no bronchioloalveolar carcinoma component (group IV). The difference between the proportion of patients with reported deaths in the time period of this study in the combined greater than 5 mm+pure invasive groups (groups III, IV), and the < 5 mm + noninvasive groups (groups I, II) is statistically significant. These results suggest that histological features may be useful in defining categories of lung adenocarcinomas with differing survival and prognostic features. These results are helpful in defining a subcategory of 'minimally invasive adenocarcinoma', which has features similar to bronchioloalveolar carcinoma.