Abstract
BACKGROUND: The incidence of pulmonary carcinoid (PC) is very rare in primary lung malignant tumors, and the prognosis of this disease is closely associated with its pathological features. In this study, the expressions of programmed death 1 (PD-1) and programmed death ligand-1 (PD-L1) in lung carcinoid cells were detected, and the correlation between the expression and corresponding clinical physiological and pathologic features was further analyzed. METHODS: The expressions of PD-1 and PD-L1 in 20 cases of PC paraffin-embedded tissue specimens were detected through immunohistochemistry. The H-score of immunohistochemical staining (range, 0-300) was employed to evaluate the expression of PD-1 and PD-L1 in the tumor tissues. RESULTS: In the 20 cases of patients with PC, 40% (8/20) showed positive expressions of PD-1, and 45% (9/20) showed positive expressions of PD-L1. Significantly higher expressions of PD-1 were observed in the smoking patients than in the nonsmoking patients (63.64% vs 11.11%, P<0.05). Furthermore, no significant relationship was found between the expressions of PD-1 and PD-L1 and the clinical characteristics of the patients, such as age, gender, pathological type, clinical stage, and metastasis (P>0.05). CONCLUSIONS: Approximately 40% of PC patients had positive expressions of PD-1or PD-L1. The positive expression rate of PD-1 in the smoking patients was significantly higher than that in the nonsmoking patients. These results suggest that the expressions of PD-1 and PD-L1 may be associated with the occurrence and development of PC.