A Case of Anti-programmed Cell Death Ligand 1 and Anti-transforming Growth Factor Beta Antibody-associated Keratoacanthoma

Keratoacanthomas (KAs) are epithelial skin tumors characterized by rapid growth and spontaneous regression, with histopathologic features similar to those of cutaneous squamous cell carcinoma (SCC). KA arising after the use of anti-programmed cell death protein 1 (PD1) and anti-transforming growth factor beta (TGF-β) antibody have been reported. The patient in the present case was administered a new anti-cancer drug under clinical trial, which comprised anti-PD-ligand 1 (PD-L1) and anti-TGF-β antibodies. Nine months after the drug was used, a hyperkeratotic nodular lesion appeared on the patient's left arm. As a result of histopathologic examination by excision of the corresponding lesion, it was diagnosed as KA.