The IL1 family member IL18 (Il18) was expressed in skin and tumor samples, but only in carcinomas did Il18 have a strong cis-eQTL, with higher expression in papillomas from susceptible animals and when a SPRET/Ei allele was present (raw P = 2.6e-8, permutation P < 0.001, q = 0.001). Here, IL18 is linked to papilloma.