In this case report, we describe a tortuous, yet rare, treatment process of the patient. The first biopsy of the patient suggested inflammatory myofibroblastic tumor, ALK (D5F3) positive. Considering the benign progression of the disease, and no indication for surgical resection, oral prednisone was given first. However, the disease rapidly progressed, and a second biopsy revealed a pulmonary sarcomatoid cancer. Since the biopsy was ALK (D5F3) positive, the effect of crizotinib treatment was significant, though crizotinib resistance unfortunately only occurred after 4 months. The third biopsy pathology was performed and confirmed lung adenocarcinoma. After switching to pembrolizumab treatment, the lesions were significantly reduced after four courses of treatment. The current condition of patient persisted in partial response.