Two Cases of Cutaneous Adverse Events Induced by Enfortumab Vedotin With Ring Mitosis: A Characteristic but Rare Histologic Finding.

Abstract: An 80-year-old man with a history of metastatic urothelial cancer involving multiple lymph nodes and the lungs received an infusion of enfortumab vedotin (EV) as third-line treatment 1 month before presentation. Thereafter, he presented with fever and diffuse erythema on the trunk and extremities. A 77-year-old man with a history of metastatic urothelial cancer involving multiple lymph nodes and bones received an infusion of EV as fourth-line treatment 10 days before presentation. He developed fever and dusky erythema on the trunk and extremities. Cutaneous biopsy specimens of the erythema of both patients showed starburst-like ring mitosis in the basal layer of the epidermis. Based on this histologic finding, erythema was diagnosed as an EV-induced cutaneous adverse event in both patients. Oral prednisolone resolved both cases of erythema. EV is an antibody-drug conjugate that inhibits microtubule polymerization. Ring mitosis has been observed in several organs, mainly the gastrointestinal tract, of patients treated with agents such as taxanes and colchicine that inhibit microtubule polymerization, similar to EV. These findings may be useful for discriminating between cutaneous adverse events caused by EV and those caused by other agents.