Histopathologic and Clinical Characterization of Brentuximab Vedotin-associated Rash.

Rash is one of the commonly observed adverse events with brentuximab vedotin (BV), a CD30-targeted antibody-drug conjugate used to treat cutaneous T-cell lymphoma (CTCL). However, clinical and histopathologic characterization of BV-associated rash (BVAR) is limited. Distinguishing BVAR from a patient's underlying CTCL can be challenging and can lead to treatment interruptions or even premature drug discontinuation. We performed a thorough clinical and histopathologic retrospective characterization of BVAR from a single institution. Utilizing polymerase chain reaction (PCR) and T-cell receptor high-throughput sequencing (TCR-HTS), we were able to isolate skin biopsy specimens from rash clinically suggestive of BVAR that also lacked a dominant TCR clone. A retrospective evaluation was performed of 26 biopsy specimens from 14 patients. Clinical features of BVAR included predominantly morbilliform or maculopapular morphology, delayed onset, and the trend toward moderate to severe classification, often requiring oral steroids. Most histopathologic specimens (25/26) showed spongiotic dermatitis as the primary reaction pattern. Many cases showed subtle findings to support a background interface or lichenoid eruption. Langerhans cell microabscesses were seen in one-fourth of specimens, and eosinophils were present in over one-half of the specimens. There were focal features mimicking CTCL, but these were not prominent. In 17 specimens with immunohistochemistry, the CD4:CD8 ratio in intraepidermal lymphocytes was relatively normal (1-6:1) in 65% (11/17) and 1:1 in 35% (6/17), demonstrating a trend toward increased CD8-positive cells compared with baseline CTCL. We have identified features that can help distinguish BVAR from a patient's CTCL, which can, in turn, help guide appropriate clinical management.