Nivolumab is commonly used as monotherapy or in combination therapy for management of locally advanced or metastatic melanoma; however, it is also associated with immunotherapy-related adverse events concerning for disease progression or tumor flare reaction. This report presents a case of a non-neoplastic pseudotumor of the lung initially mistaken for malignancy that occurred in a patient receiving adjuvant nivolumab therapy following complete resection of stage IIIB melanoma. The diagnosis was made by lung biopsy and confirmed by a wedge resection, with findings consistent with organizing pneumonia type of pulmonary inflammatory pseudotumor rather than malignancy.
Keywords: immunotherapy; melanoma; pseudotumor.
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