Rapidly Growing <scp>ALK</scp> ‐Negative <scp>NTRK3</scp> ‐Positive Inflammatory Myofibroblastic Tumour of the Lung

Inflammatory myofibroblastic tumours (IMT) are rare mesenchymal neoplasms that account for less than 1% of all lung tumours. Although ~50%-60% of IMT cases are anaplastic lymphoma kinase (ALK)-positive, ALK-negative IMT cases present diagnostic challenges owing to diverse pathological features. Here, we report a rare case of a rapidly growing ALK-negative, neurotrophic tyrosine receptor kinase 3 (NTRK3)-positive pulmonary IMT in a 46-year-old man with a history of pulmonary tuberculosis. A 13-mm nodule detected during routine screening grew to 18 mm within 1 month. Complete surgical resection was performed by video-assisted thoracic surgery. Histopathological examination revealed spindle cell proliferation with inflammatory cell infiltration. Immunohistochemistry was negative for ALK; however, molecular analysis identified an ETV6-NTRK3 fusion gene. The patient remains disease-free at 9 months postoperatively. This case highlights the importance of comprehensive molecular testing in ALK-negative IMT and demonstrates that complete surgical resection can achieve excellent outcomes even in rapidly growing lesions.