TRIM21 and pachyonychia congenita: We performed Immunohistochemistry (IHC) analysis on adjacent non‐cancerous and cancerous tissues (n = 60), serous cystadenomas (n = 33) and solid pseudopapillary neoplasms (SPN, n = 26), and the expression of TRIM21 in PC tumor tissues is higher than that in the other three types of tissues (Figure 1F,G, Figure S1D, Supporting Information).