In general, PTCs are classified into conventional PTC (CPTC), follicular variants PTC (FVPTC), tall-cell PTC (TCPTC), and other rare variants based on their distinct pathological features, growth patterns and behaviors.17 TCPTC is more aggressive and the prevalence of BRAFV600E mutation is ~100%, while its prevalence in FVPTCs is relatively low.2,18 This was supported by the data from TCGA dataset that CYP2S1 expression was much higher in TCPTCs than FVPTCs and normal controls (Fig. 1c). This evidence concerns the gene CYP2S1 and follicular variant thyroid gland papillary carcinoma.