Case Report: Lenvatinib-induced lichenoid drug reaction mimicking disseminated zoster in a patient with metastatic hepatocellular carcinoma.

Lenvatinib, a multi-kinase inhibitor targeting VEGFR 1-3 and FGFR 1-4, is a first-line therapy for unresectable hepatocellular carcinoma (HCC). While palmar-plantar erythrodysesthesia and generalized erythematous rashes are recognized side effects, lenvatinib-induced lichenoid drug reactions (LDRs) remain infrequently reported and pose significant diagnostic challenges when presenting as viral exanthematous mimics. This case describes an 82-year-old female with metastatic HCC who developed a generalized, pruritic, and vesicular rash mimicking disseminated herpes zoster shortly after initiating lenvatinib. Despite prior shingles vaccination, empiric intravenous acyclovir was initiated. A skin biopsy revealed a lichenoid dermatitis with Civatte bodies and significant eosinophilia, confirming an LDR. The eruption resolved following systemic corticosteroid therapy, indicating a likely reaction to recent lenvatinib exposure. This case highlights the importance of histopathological verification and chronological drug reconciliation in differentiating drug-induced dermatotoxicity from viral exanthems in fragile oncology populations.