The subgroup analysis of tumor type demonstrated negative impact of elevated MDK on OS in most solid tumor patients (P < 0.05), while MDK had no relevance with OS in the patients with OSCC (pooled HR = 1.68; 95% CI = 0.84–3.36; P = 0.145) or HNSCC (pooled HR = 1.56; 95% CI = 0.96–2.51; P = 0.075). Here, MDK is linked to head and neck squamous cell carcinoma.