Invasive adenocarcinoma intraoperatively misdiagnosed as adenocarcinoma in situ or minimally invasive adenocarcinoma is more likely to undergo potentially insufficient resection. The purpose of our study was to evaluate the diagnostic accuracy of frozen section. We retrospectively reviewed 1,111 lung adenocarcinomas from January to March 2016 to evaluate the diagnostic performance of frozen section. A derivation cohort consisting of 436 cases of adenocarcinoma in situ or minimally invasive adenocarcinoma diagnosed by frozen section in the same period were analyzed to find predictive factors for invasive adenocarcinoma as the final diagnosis. Validation cohorts (first: April to June 2016, second: January to March 2015) were included to confirm the results. The overall concordance rate between frozen section and final diagnosis was 92%. Most frozen section errors were underestimation. The sensitivity of frozen section diagnosis for minimally invasive adenocarcinoma (74%) was significantly lower than others. Intraoperatively measured tumor size was the only independent factor for invasive adenocarcinoma as the final diagnosis (<1 cm: 2%, reference; 1-1.4 cm: 15%, odds ratio, 5.678; > 1.5 cm: 18%, odds ratio, 5.878; P = 0.001) in the derivation cohort, and was confirmed by validation cohorts. Fifty-nine misdiagnosed invasive adenocarcinomas in the three cohorts consisted of 54 lepidic predominant type, 1 papillary and 4 acinar predominant type. There were no positive N1, N2 node, pleural, lymphatic and vascular invasion cases found. Thirty-seven (37/59, 63%) cases of misdiagnosis were attributed to sampling error, which was the main reason. Our study suggests that adenocarcinoma in situ or minimally invasive adenocarcinoma ≥1 cm by frozen section were more likely to be invasive adenocarcinoma because of sampling error. Frozen section diagnosis of adenocarcinoma in situ or minimally invasive adenocarcinoma should be considered cautiously for tumors ≥1 cm to avoid potentially insufficient resection.

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Background There is scant evidence‐based information about survival benefits of postoperative chemotherapy in elderly patients with early‐stage non‐small cell lung cancer (NSCLC). The purpose of this study is to compare the overall survival (OS) and cancer‐specific survival (CSS) rates of surgery alone versus postoperative chemotherapy in patients aged ≥70 years with stage I‐II NSCLC. Methods Elderly patients aged ≥70 years diagnosed with stage I‐II NSCLC were selected from the Surveillance, Epidemiology, and End Results (SEER) database from January 1, 2010 to December 31, 2015. OS and CSS were compared between the two groups utilizing overlap weighting analysis, inverse probability of treatment weight (IPTW), and propensity score matching (PSM). Results Of the 7193 included patients with stage I‐II NSCLC who are more than 70 years old, 681 patients (9.5%) received postoperative chemotherapy and 6512 patients (90.5%) received surgery‐alone. Median OS was 77 months in postoperative chemotherapy group versus 79 months in surgery‐alone group (p = 0.89). The result of IPTW analysis showed the similar results. The probability of patients choosing chemotherapy increased with the AJCC stage and Grade increasing (p < 0.001) and decreased with the growth of age (p < 0.001). The results of subgroup analysis showed that the survival rate of stage IA patients decreased significantly after postoperative chemotherapy (p < 0.01) while the survival rate of stage IB‐II patients increased significantly (p < 0.01). At the same time, we found that patients in the postoperative chemotherapy group tended to have better OS than those in the surgery‐alone group with the grade and tumor size increasing. Conclusion The results of this study indicated that postoperative chemotherapy could significantly improve the survival of stage IB‐II NSCLC patients aged ≥70 years, and decrease the survival of stage IA patients.