With the expansion of immunotherapy in the treatment of lung cancer, clinicians have to face new clinical pictures and adapt their practice. We report the case of a 69-year-old man diagnosed with non-small cell lung cancer using endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) and treated with nivolumab as second-line therapy. After 8 injections of nivolumab, a new CT and PET scan revealed massive growth and increase in metabolism of hilar and mediastinal lymph nodes, whereas the size and metabolism of the left upper lobe lesion were reduced. A new EBUS-TBNA was thus performed and showed an epithelioid cell reaction compatible with sarcoidosis in the 3 punctured lymph nodes (stations 4R, 11L, 7). In the absence of cancer evolution, nivolumab was continued, and the CT after the twelfth injection showed stability.