Abstract: Objective: To study the clinicopathological features and prognostic significance of different pathological subtypes of T₁ invasive lung adenocarcinoma for providing a reference for the monitoring and treatment strategy of lung adenocarcinoma. Methods: A total of 120 patients undergone surgical treatment and confirmed by postoperative pathology as invasive lung adenocarcinoma with tumor diameter less than or equal to 3 cm from Jan. 2009 to Jan, 2011 were enrolled. The patients were divided into five groups according to dominant pathological subtypes: lepidic group,acinar group, papillary group, micro-papillary group, and solid group. The clinical and pathological data of the patients were analyzed retrospectively. Kaplan-Meier method was used to calculate survival rate. Log-Rank test was used to compare survival difference. COX regression analysis was used to determine the risk factors of prognosis. Result: There were no significant differences in age, sex, CEA level and tumor differentiation between the five groups（P>0.05）. Meanwhile, there were significant differences in invasion of visceral pleura, lymph node metastasis, TNM stage and recurrence or metastasis after operation between the five groups（P<0.05）. Among the five subtypes, lymph node metastasis rate (62.5%) and postoperative recurrence rate (41.6%) were the highest in micro-papillary group. Survival analysis showed that lipidic group had the best prognosis, the 5 year survival rate was 96.0%; the prognosis of micro-papillary group was the worst, and the 5 year survival rate was 66.7%. The difference was statistically significant（P<0.05）. Pathological subtypes, lymph node metastasis and TNM staging were the risk factors influencing the prognosis of stage T₁ invasive lung adenocarcinoma. Different pathological subtypes and lymph node metastasis were the independent prognostic factors (OR>1). Conclusions: The prognosis of T₁ invasive adenocarcinoma of lung is related to pathological subtype and lymph node metastasis. Micro-papillary subtypes indicate higher lymph node metastasis and poor prognosis. More aggressive treatment and observation might be needed after operation of micro-papillary subtype of invasive lung adenocarcinoma.

Key words: Lung adenocarcinoma, T₁, Prognosis, Pathological subtype