The effect that pathologic and radiologic interpretation of invasive and non-invasive areas in lung adenocarcinoma has on T-stage and treatment.

Lung adenocarcinoma is currently staged based on invasive tumor size, excluding areas of lepidic (in situ) growth. Invasive tumor size may be determined by pathologic assessment of a surgical specimen or radiographic assessment on computerized tomography (CT) scan. When invasive tumor size is the primary stage determinate, radiographic-pathologic discordance or discordant interpretation among pathologists may alter tumor stage and treatment. We reviewed 40 cases of non-mucinous pulmonary adenocarcinoma in which tumor size was the only stage-determinant. We determined the inter-observer variability when microscopically assessing architectural patterns and its effect on pathologic stage and treatment. Additionally, we correlated pathologic and radiographic assessment of invasive tumor size and its effect on tumor stage and treatment. The intraclass correlation among three pathologists was 0.9879; all three pathologists agreed on T-stage in 75% of cases. Four cases of pathologic disagreement had the potential to alter therapy. Intraclass correlation between the pathologists and invasive tumor size determined by CT scan was 0.8482. In 23 cases (57.5%) the pathologic T-stage differed (it increased >90% of the time) from clinical T-stage (determined by CT scan) based on invasive tumor size. Five of the radiographically-pathologically discrepant cases resulted in a stage change that had the potential to alter adjuvant therapy. Our findings suggest the stage differences in pathologic staging are prognostically relevant, but unlikely to impact routine selection of adjuvant therapy, and the observed variability in clinical stage tends to select against overuse of neoadjuvant therapy when invasive tumor size is the primary stage-determinant.