Although prognosis and treatments differ between small-cell- and nonsmall-cell carcinoma, comparisons of the histological types of NSCLC are uncommon. Thus, we investigated the oncological factors associated with the prognosis of early-stage adenocarcinoma and squamous cell carcinoma. We retrospectively compared the clinicopathological backgrounds and postoperative outcomes of patients diagnosed with pathological stage I–IIA adenocarcinoma and squamous cell carcinoma primary lung cancer completely resected at our department from January 2007 to December 2017. Multivariable Cox regression analysis for overall survival and recurrence-free survival was performed. The median follow-up duration was 55.2 months. The cohort consisted of 532 adenocarcinoma and 96 squamous cell carcinoma patients. A significant difference in survival was observed between the two groups, with a 5-year overall survival rate of 90% (95% confidence interval 86–92%) for adenocarcinoma and 77% (95% CI 66–85%) for squamous cell carcinoma (P < 0.01) patients. Squamous cell carcinoma patients had worse outcomes compared to adenocarcinoma patients in stage IA disease, but there were no significant differences between the two groups in stage IB or IIA disease. In multivariate analysis, invasion diameter was associated with overall survival in adenocarcinoma (hazard ratio 1.76, 95% confidence interval 1.36–2.28), but there was no such association in squamous cell carcinoma (hazard ratio 0.73, 95% confidence interval 0.45–1.14). The importance of tumor invasion diameter in postoperative outcomes was different between adenocarcinoma and squamous cell carcinoma. Thus, it is important to consider that nonsmall-cell carcinoma may have different prognoses depending on the histological type, even for the same stage.

Small cell lung cancer (SCLC) and large cell neuroendocrine carcinoma (LCNEC) have recently been grouped as lung neuroendocrine carcinomas (NECs). Because these lung NECs are clinically malignant and their treatment strategies differ from those of non-SCLC, the quality of diagnosis has a significant prognostic impact. The diagnosis of LCNEC requires positive immunohistochemical staining with chromogranin A, synaptophysin, and CD56, along with a morphological diagnosis, and insulinoma-associated protein 1 (INSM1) has been proposed as an additional marker but is still not an ideal or better marker. We investigated Musashi-1 as a novel immunohistochemical marker in 42 patients with SCLCs and 44 with LCNECs who underwent lung resection between 1998 and 2020 at our institution. We found Musashi-1 expression in 98% (41/42) SCLC and in 90% (40/44) LCNEC. These findings were similar to CD56 expression and superior to synaptophysin, chromogranin A, and INSM1. Musashi-1 also tended to show more diffuse and intense staining, especially in LCNEC, with more cases staining > 10% than any other existing markers (Musashi-1, 77%; INSM1, 45%; chromogranin A, 34%; synaptophysin, 41%; and CD56, 66%). In conclusion, we identified Musashi-1 as a novel immunohistochemical staining marker to aid in the diagnosis of lung NEC.

Small cell lung cancer (SCLC) and large cell neuroendocrine carcinoma (LCNEC) have recently been grouped as lung neuroendocrine carcinomas (NECs). Because these lung NECs are clinically malignant and their treatment strategies differ from those of non-SCLC, the quality of diagnosis has a significant prognostic impact. The diagnosis of LCNEC requires positive immunohistochemical staining with chromogranin A, synaptophysin, and CD56, along with morphological diagnosis, and insulinoma-associated protein 1 (INSM1) has been proposed as an additional marker but sometimes experience difficulty in making the diagnosis. We investigated Musashi-1 as a novel immunohistochemical marker in 42 patients with SCLCs and 44 with LCNECs who underwent lung resection between 1998 and 2020 at our institution. We found Musashi-1 expression in 41 (98%) of 42 SCLCs and 40 (90%) of 44 LCNECs. These findings were similar to CD56 expression and superior to synaptophysin, chromogranin A, and INSM1. Musashi-1 also tended to show more diffuse and intense staining, especially in LCNEC, with more cases staining >10% than any other existing markers (Musashi-1, 77%; INSM1, 45%; chromogranin A, 34%; synaptophysin, 41%; and CD56, 66%). In conclusion, we identified Musashi-1 as a novel immunohistochemical staining marker to aid in the diagnosis of lung NEC.