Sarcoid-like reactions in patients treated with checkpoint inhibitors for advanced solid tumors.

While new intrathoracic adenopathy in a patient with cancer can represent progression of disease, the differential diagnosis is broad. Sarcoid-like reactions (SLR) remain an underreported source of lymphadenopathy in patients treated with immune checkpoint inhibitors (ICI), with limited reports in patients with cancers other than melanoma. To characterize SLRs among patients treated with ICI for advanced solid tumors. Data were collected on the clinical, pathologic, and radiographic presentation of patients treated with ICI who developed clinical or imaging findings suggestive of an SLR, including the presence of hilar or mediastinal lymphadenopathy, cutaneous/subcutaneous involvement, and/or worsening of existing sarcoidosis on ICI. Twelve patients were identified as having experienced an SLR. While 6 patients had melanoma, SLRs were also observed among patients with lung, gynecologic, and genitourinary cancers, including high-grade serous ovarian carcinoma, and an angiomyolipoma. Median time from initiation of ICI to diagnosis of an SLR was 3.4 months (range: 1.8-9.1). All but one patient (92%) were deemed to have had a radiographic response to ICI. Clinicians should maintain the awareness of the possibility of SLRs in patients receiving ICI, particularly in patients whose scans show evidence of "mixed" response, with decreases in certain lesions coupled with new/increasing intrathoracic lymphadenopathy and/or other systemic signs of sarcoid.