Is CK7 a Prognostic Marker in Pulmonary LCNEC? Evidence from a Limited Cohort Study

<b>Objectives:</b> While the treatment of non-small-cell lung carcinoma has improved rapidly, the treatment of pulmonary large-cell neuroendocrine carcinoma (LCNEC) remains underdeveloped. The use of immunohistochemistry allows for accurate risk stratification. With our study, we investigated the outcome of patients with pulmonary LCNEC and analyzed whether CK7 correlates with long-term survival. <b>Methods:</b> We retrospectively collected the monocentric data of patients which underwent anatomical resection for lung cancer between January 2012 and December 2020. Patients that did not show pulmonary LCNEC or adenocarcinoma, had a positive resection margin, or underwent neoadjuvant therapy were excluded. The long-term survival rate of the LCNEC and adenocarcinoma groups were compared before and after propensity score matching. Furthermore, we performed survival analyses for a subgroup of LCNEC distinguished by CK7 expression, followed by Cox regression analyses. <b>Results:</b> A total of 466 patients were integrated for further analysis. The mean age was 65.3 ± 9.6 years. There were no significant differences between both groups regarding age, gender, or comorbidities. In terms of the UICC stage, the groups were equally distributed. Mean survival in the LCNEC group was significantly worse than in the adenocarcinoma group (LCENC: 36.4 ± 7.5 months; adenocarcinoma: 80.7 ± 8.1 months; <i>p</i>-value = 0.001). The mean survival rate was 19.23 ± 4.8 months in the CK7 expression group and 57.01 ± 8.5 months in the group without expression, which reached statistical significance (<i>p</i>-value = 0.019). <b>Conclusions:</b> Our study suggests that pulmonary LCNEC has a significantly worse prognosis than pulmonary adenocarcinoma. CK7 expression seems to be correlated with a worse outcome for the long-term survival rate of patients suffering from highly malignant pulmonary LCNEC.