DSG1 and non-small cell lung carcinoma: SELL, ACTB, DSG1, and PODXL were in cluster A, suggesting they are tightly connected with BM in NSCLC, which was discovered by comparing these 22 distinct proteins with those in clusters A and B. ROC curves suggested that SELL, DSG1 and PODXL proteins might be used as biomarkers for BM detection in NSCLC patients, and the trio together had a higher diagnostic value (AUC = 0.844) (Additional file 4: Figure S3C, D).