Lichenoid dermatitis from immune checkpoint inhibitor therapy: An immune‐related adverse event with mycosis‐fungoides‐like morphologic and molecular features

Abstract

Cutaneous immune-related adverse events (irAEs) are a known consequence of immune checkpoint inhibitor (ICI) therapy and may exhibit a spectrum of morphologic features both clinically and histologically. Lichenoid dermatitis associated with ICI therapy (LD-ICI) is the most frequently encountered histopathologic type of irAE biopsied by dermatologists. There is frequent clinical and histologic overlap between irAEs and several reactive and neoplastic dermatologic disorders; thus, clinical information is essential. LD-ICI with histologic, immunohistochemical, and molecular features typical of mycosis fungoides (MF) are unique. Here, we report a patient who developed LD-ICI with MF-like morphologic features with monoclonal T-cell receptor gene rearrangement on consecutive biopsies during ICI therapy. The development of monoclonal LD-ICI is important for clinicians and pathologists to recognize in patients receiving ICI therapy. K E Y W O R D S dermatologic toxicity, immune checkpoint inhibitor, immune-related adverse events, lichenoid dermatitis, mycosis fungoides

Hypertrophic lichenoid dermatitis immune‐related adverse event during combined immune checkpoint and exportin inhibitor therapy: A diagnostic pitfall for superficially invasive squamous cell carcinoma

“…LD‐irAE is an inflammatory, immune‐mediated process and is the most common morphology biopsied (approximately 54%‐95% of all cutaneous irAE biopsies) in patients receiving ICI therapy 7,14 . While the immunopathogenesis of LD‐irAEs needs further investigation, contributing factors may include altered cutaneous microbiome and activation of the innate immune response along with involvement of the Toll‐like receptor (TLR)/CD14‐mediated pathway in susceptible patients 16 .…”

“…The development of LD‐irAE from ICI therapy usually occurs at ~3 months after initiation of ICI therapy, but may range from a few weeks to several months 8 . LD‐irAE lesions usually present as erythematous patches and papules that coalesce into plaques and infrequently as exuberant nodules that may mimic superficially invasive SCC 7,11 …”

“…Approximately 20% to 50% of patients receiving ICI therapy may develop irAEs and include several types of clinical presentations. Cutaneous reactions may be inflammatory or immunobullous and lesions may lead to alteration of epidermal keratinocytes and melanocytes 6‐8 . Lichenoid dermatitis irAE (LD‐irAE) is common in patients receiving ICI therapy and histopathologically may appear identical to lichen planus (LP) and other LD unrelated to ICI therapy 6,7,9 .…”

“…Cutaneous reactions may be inflammatory or immunobullous and lesions may lead to alteration of epidermal keratinocytes and melanocytes 6‐8 . Lichenoid dermatitis irAE (LD‐irAE) is common in patients receiving ICI therapy and histopathologically may appear identical to lichen planus (LP) and other LD unrelated to ICI therapy 6,7,9 . Hypertrophic LD‐irAE is a unique variant that shows irregular epidermal hyperplasia with hypermaturation, orthohyperkeratosis and some keratinocytic atypia, similar to hypertrophic LP, 8‐10 or well‐differentiated squamous cell carcinoma (SCC) with minimal keratinocytic atypia.…”

Clinical management of immune-related adverse events following immunotherapy treatment in patients with non-small cell lung cancer

“…While not usually severe, the dry skin, itching and flaking resulting from ICIs are among the most common complaints from treated patients. While multiple types of dermatitis can present following inhibitor treatment, the most commonly encountered histopathologic type of irAE biopsied by dermatologists is ICI-related lichenoid dermatitis,30 detected in 50% of biopsy specimens from this population. Histologically it appears as band-like lymphocytic infiltrate in the papillary dermis with epidermal necrosis, and spongiotic dermatitis (40%) characterized by epidermal spongiosis with lymphocytic infiltrate surrounding the vessels of the superficial plexus with the presence of eosinophils 31.…”