Prognostic Significance of Predominant Histologic Pattern and Nuclear Grade in Resected Adenocarcinoma of the Lung Potential Parameters for a Grading System

Introduction: Currently, no agreed histologic grading system exists for lung adenocarcinomas (ADCs). With a recently updated consensus classification, the aim of this study was to assess potential prognostic factors identifiable on routine histology, which might be used as grading parameters. Methods: A retrospective study of resected pulmonary ADCs (n = 238) in patients with stage IA to IIIB disease was carried out in which various histopathological parameters were correlated with survival data. The relationship between these factors and patient survivability was analyzed using Cox proportional hazards regression. Results: Mitotic rate was found to be a highly significant prognostic marker (p = 0.008), as was overall nuclear grade (p < 0.001). ADC subtyping was also found to be potentially important, as lepidic predominant (hazard ratio 0.99, p = 0.023) and solid predominant (hazard ratio 1.01, p = 0.003) subtypes were found to be independent (to age and tumor, node, metastasis category) prognostic predictors. Vessel invasion within tumor approached significance as a negative prognostic factor (p = 0.067). Conclusions: This study showed not only that histologic subtype and mitotic rate are important prognostic factors in lung ADCs, but also that other criteria described previously may not be useful in our specific patient population.