A retrospective study revealed that the pathological response rate of selecting PC when TIMP1 immunostaining was high and selecting SC when TIMP1 immunostaining was low/negative was 80.0%, and the pathological response rate of selecting SC when DSG2 immunostaining was high and selecting PC when DSG2 immunostaining was low was 88.9% (Table 5). This evidence concerns the gene TIMP1 and pachyonychia congenita.