Blood and Histopathological Biomarkers of Immune-related Adverse Effects of Treatment with Immune Checkpoint Inhibitors

Abstract

Histopathology A skin biopsy is usually done for any atypical, severe, persistent, recurrent or poorly tolerated rash following ICI treatment [1]. Histopathological examinations of skin biopsies from many patients have shown the presence of perivascular lymphocytic infiltrates going deep into the dermis, patchy necrotic keratinocytes, and few to a large number of eosinophils [1] with CD4 + and CD8 + T cells in close proximity to melanocytes [4,5]. Other characteristic histopathologic aspects can be similar to those seen in patients with psoriasis, Grover's disease, bullous pemphigoid, and granulomatous sarcoidlike dermatitis. Less commonly, a lichenoid reaction can be seen, and this is particularly common with anti-PD-1/PD-L1 agents [1]. Some patients may have vitiligo like lesions, but these lesions have a different pathophysiological mechanism, as reported by Larsabal M et al. They recently reported that the vitiligo-like lesions that develop as adverse effects of ICI differ histologically, particularly with regard to the presence ofskin infiltration by CD8 + T-cells expressing C-X-C motif receptor 3, which is not seen in true vitiligo [6].