Basal cell tumors were superficially wounded or exposed to 24-hour occlusive applications of 0.5% resin podophyllum in alcoholic solution. These stimuli did not induce the tumor cells to participate in the healing process nor to show any detectable sign of keratinization. These observations support the hypothesis that basal cell tumors are derived from cutaneous epithelial cells which have lost the capacity of keratinization.
Waldorf DS, Van Scott EJ. Inability to Induce Keratinization in Basal Cell TumorsWounding and Application of Resin Podophyllum. Arch Dermatol. 1967;95(6):576-582. doi:10.1001/archderm.1967.01600360022003