BI24 Cutaneous pseudolymphoma secondary to pembrolizumab

Abstract A 35-year-old man presented with a 7-week history of itchy, nontender, indurated erythematous plaques and nodules on his forehead upper back, no discriminatory clinical features. He was systemically well. Three months previously, he had completed 12-month course adjuvant pembrolizumab for stage IIIC melanoma. The primary melanoma been excised from left cheek, involvement parotid supraclavicular lymph nodes, treated clearance via superficial parotidectomy neck dissection. Clinical imaging surveillance revealed evidence recurrence. Incisional biopsies the lesions back both demonstrated deep dermal perivascular periadnexal infiltrate small- medium-sized lymphoid cells. There epidermotropism B- T-cell clonality studies were negative. Morphological appearance immunophenotype favoured CD4+-reactive process in keeping cutaneous pseudolymphoma (CPL), secondary to pembrolizumab. conspicuous lesion unresponsive clobetasol propionate under occlusion. single intralesional triamcinolone acetonide 10 mg mL–1 resulted significant improvement within days, subsequent complete resolution. resolved spontaneously. Drug-induced CPL describes an adverse drug reaction mimicking or lymphomas clinically and/or histologically. It has described anticonvulsants, antidepressants biologic agents, often resolution cessation responsible (Etesami I, Kalantari Y, Tavakolpour S et al. pseudolymphoma: systematic review literature. Australas J Dermatol 2023; 64:41–9). proposed that drugs affect immune surveillance, leading abnormal lymphocyte response. case report (Ayoubi N, Haque A, Vera N Ipilimumab/nivolumab-induced patient malignant Cutan Pathol 2020; 47:390–3) drug-induced ipilimumab nivolumab 38-year-old presenting hands face, similar presentation our patient, which responded prednisolone. As other effects immunotherapy, it is likely this cohort due iatrogenic dysregulation overactivity. We present first reported highlight successful use steroid as treatment option. important recognize effect immunotherapy be aware can after completing ongoing