Co-expression of K5 and K6 has been reported in a number of different types of neoplasms including basal cell carcinoma [33], prostate cancer [34, 35], ductal breast carcinoma [36–38], mesothelioma [39, 40], lung carcinomas [41], melanoma, basal cell carcinoma, and salivary gland tumors [22]. This evidence concerns the gene KRT5 and mesothelioma.