SIGLEC9 and head and neck squamous cell carcinoma: TCGA and GTEx databases revealed that SIGLEC9 is strongly expressed in numerous tumors, including breast cancer, gliomas, head and neck squamous cell carcinoma (HNSC), kidney tumors, stomach adenocarcinoma (STAD), thyroid carcinoma (THCA), cervical cancer, esophageal carcinoma (ESCA), ovarian cancer, skin cutaneous melanoma (SKCM), testicular germ cell tumors (TGCT), or uterine cancer [3].