Granulomatous/sarcoid-like reactions in the setting of programmed cell death-1 inhibition: a potential mimic of disease recurrence.

Nivolumab and pembrolizumab are humanized IgG4 monoclonal antibodies against programmed cell death 1 (PD-1). Although these agents are effective in treating advanced melanoma, non-small-cell lung carcinoma, and other types of cancers, various adverse events have been reported. Cutaneous adverse events are particularly prevalent and, while granulomatous/sarcoid-like reactions are uncommon, they are increasingly recognized as immune-related adverse events associated with immune checkpoint inhibitors. Herein, we report two cases of granulomatous/sarcoid-like reaction with foreign material, mimicking metastatic malignancy after PD-1 inhibitor treatment. Clinicians should be aware of the existence of cutaneous lesions and perform biopsy if needed to prevent misdiagnosis and unnecessary adjustments to immunotherapy.