OBJECTIVETo study the prognostic significance of grading system for stromal invasion in pathologic tumor stage T1 (pT1) adenocarcinoma of lung.

METHODSEighty-five cases of surgically resected pT1 lung adenocarcinoma with clinicopathologic and follow-up data were retrospectively reviewed. The degree of invasive growth was classified into three grades according to its location in the tumor. The clinicopathologic characteristics and prognostic significance were analyzed.

RESULTSAmongst the 85 cases studied, 17 cases (20%) were in grade 1, 12 (14%) in grade 2 and 56 (66%) in grade 3. The tumor size was smaller and lymphovascular permeation was less frequently encountered in cases with grade 1 stromal invasion than in those with grade 3 (P=0.005 for tumor size and P=0.018 for occurrence of lymphovascular permeation). The rate of lymph node metastasis and pathologic staging in cases with grade 1 and grade 2 were similar and were significantly lower than those with grade 3 (P=0.007 for rate of lymph node metastasis in grade 1 versus grade 3 tumors, P=0.002 for pathologic stage in grade 1 versus grade 3 tumors, P=0.027 for rate of lymph node metastasis in grade 2 versus grade 3 tumors and P=0.021 for pathologic stage in grade 2 versus grade 3 tumors). There was no statistically significant difference with respect to age, gender and smoking history of the patients, amongst cases in different grades. The overall five-year survival rate was 63%. The five-year survival rates for cases with grade 1, grade 2 and grade 3 were 100%, 83.3% and 46.6%, respectively. The difference between cases with grade 2 and grade 3 was statistically significant (P=0.027). The death rate during follow-up for cases with grade 1, grade 2 and grade 3 were 0, 16.7% and 42.9%, respectively. The difference between cases with grade 1 and grade 3 was statistically significant (P=0.001). Univariate analysis showed that grade of stromal invasion (P=0.001), pathologic stage (P<0.001), presence of lymphovascular permeation (P<0.001) and lymph node involvement (P<0.001) represented important prognostic factors. Multivariate analysis also showed that pathologic stage (P<0.001) was an independent prognostic factor.

CONCLUSIONSThe grading system of stromal invasion in pulmonary adenocarcinoma correlates with tumor prognosis and other prognostic factors. It represents a useful criterion in prognostic categorization of pT1 adenocarcinoma of lung.