Significant heterogeneity was noted in the relationships between Cystatin D and lung adenocarcinoma (Q = 33.837, p < 0.001), Cystatin M (prot‐a‐703), and squamous cell lung carcinoma (Q = 25.73, p = 0.002), and Cystatin F and NSCLC (Q = 22.881, p = 0.029) (Table 2). Here, CST6 is linked to squamous cell lung carcinoma.