Expression of fDEGs was frequently decreased from primary carcinoma to nodal metastases except for SPHK1 in matched pairs of primary carcinoma and cervical lymph node metastases of treatment-naïve, HPV-negative HNSCC in external dataset GSE188737 [17] (Suppl. The gene discussed is SPHK1; the disease is head and neck squamous cell carcinoma.