Transformation of invasive lung adenocarcinoma with ALK rearrangement into pulmonary sarcomatoid carcinoma

Background Anaplastic lymphoma kinase (ALK) tyrosine kinase inhibitors (TKIs) improve outcomes for non-small-cell lung cancer (NSCLC) patients with ALK fusions. Nevertheless, ALK TKI resistance will inevitably occur. Histological transformation is one of the causes of TKI resistance in NSCLC. Reports of ALK-rearranged adenocarcinoma with histological transformation are limited. Case presentation A case of an invasive lung adenocarcinoma patient with ALK rearrangement who experienced histological transformation into sarcomatoid carcinoma after ALK TKI resistance is reported, and ALK fusion, MET amplification and TP53 mutation were detected after transformation. Conclusions This case first reported a patient with invasive lung adenocarcinoma harboring ALK rearrangement who underwent histological transformation into sarcomatoid carcinoma after ALK TKI resistance, and MET amplification might represent the cause. After transformation, the patient benefited from targeted therapy combined with chemotherapy, which represents a promising option for patients with sarcomatoid carcinoma transformation.