TACR1 and cancer: SP/NK-1R showed a high expression in a relevant proportion of cases in head and neck tumorigenesis (benign and malignant tumors and pre-malignant tissues) (PP = 40.52%, 95%CI = 24.23–57.78) (Figure 3, Table 2), although a considerable degree of heterogeneity was present (p < 0.001, I2 = 96.89%), indicating that all tumors do not display similar expression levels.