Resolution of Paraneoplastic Cutaneous Angioendotheliomatosis After CAR T‐Cell Therapy in TP53‐Deleted CLL: A Case Report

ABSTRACT Cutaneous manifestations of chronic lymphocytic leukemia (CLL) are heterogeneous and may result from leukemic infiltration, secondary malignancies, infectious complications, or reactive inflammatory processes. Reactive angioendotheliomatosis (RAE) is a rare vascular proliferation that has only infrequently been reported in association with hematologic malignancies. We describe a 58‐year‐old man with high‐risk relapsed/refractory CLL harboring TP53 mutation and del(17p) who developed rapidly enlarging, fungating cutaneous lesions involving the right thumb, upper arm, and additional sites despite multiple prior therapies, including fludarabine, cyclophosphamide, rituximab, ibrutinib, and venetoclax. Histopathologic evaluation demonstrated dermal vascular proliferation with endothelial marker positivity (CD31, CD34, ERG, and vimentin), consistent with RAE and without evidence of leukemic infiltration. The lesions were refractory to local supportive measures but showed marked regression following treatment with CD19‐directed chimeric antigen receptor (CAR) T‐cell therapy using lisocabtagene maraleucel. Notably, cutaneous remission despite persistent measurable residual disease and eventual systemic relapse requiring allogeneic hematopoietic cell transplantation. This discordance suggests that regression of RAE may be mediated through immune modulation and alteration of inflammatory or angiogenic pathways rather than direct elimination of cutaneous leukemia. To our knowledge, this is among the first reports describing resolution of paraneoplastic RAE following CAR T‐cell therapy in CLL, and it highlights the broader immunomodulatory effects of cellular immunotherapy beyond direct antitumor activity. Trial Registration The authors have confirmed clinical trial registration is not needed for this submission