Prognostic Effects of Predominant Histologic Subtypes in Resected Pulmonary Adenocarcinomas

BACKGROUND: Predominant histologic subtypes have been reported as predictors of survival of patients with pulmonary adenocarcinoma. AIMS: To evaluate the predictive value of histologic classification in resected lung adenocarcinoma using the classification systems proposed by the International Association for the Study of Lung Cancer, American Thoracic Society, European Respiratory Society, and World Health Organization (2015). STUDY DESIGN: Cross-sectional study. METHODS: The histologic classification of a large cohort of 491 patients with resected lung adenocarcinoma (stages I-III) was retrospectively analyzed. The tumors were classified according to their predominant component (lepidic, acinar, papillary, solid, micropapillary, and mucinous), and their predictive values were assessed for clinicopathologic characteristics and overall survival. RESULTS: The patient cohort comprised 158 (32.2%) patients with solid predominant, 150 (30.5%) with acinar predominant, 80 (16.3%) with papillary predominant, 75 (15.3%) with lepidic predominant, 22 (4.5%) with mucinous, and 5 (1.0%) with micropapillary subtype, and 1 (0.2%) with adenocarcinoma in situ. Overall 5-year survival of 491 patients was found to be 51.8%. Patients with lepidic, acinar, and mucinous adenocarcinoma had 70.9%, 59.0%, and 66.6% 5-year survival, respectively, and there was no statistically significant difference between them. Whereas patients with solid, papillary, and micropapillary predominant adenocarcinoma had 41.0%, 40.5%, and 0.0% 5-year survival, respectively. Compared to other histologic subtypes, patients with solid and papillary predominant adenocarcinoma had significantly lower survival than those with lepidic (p<0.001, p=0.002), acinar (p<0.001, p=0.008), and mucinous (p=0.048, p=0.048) subtypes, respectively. The survival difference between patients with solid subtype and those with papillary subtype was not statistically significant (p=0.67). CONCLUSION: Solid and papillary histologic subtypes are poor prognostic factors in resected invasive lung adenocarcinoma.