We report a case of pulmonary inflammatory myofibroblastic tumor (IMT) showing aggressive and unusually rapid progression. A 27-year-old woman was admitted to the emergency room due to dry cough, fever and blood-tinged sputum that lasted one week. Initial chest radiograph and computed tomography scan revealed multifocal pulmonary nodules, which subsequently progressed into large necrotic masses within two months. She underwent a fine needle biopsy of the largest mass in the right middle lung zone which revealed inflammatory myofibroblastic cells consistent with IMT. The masses showed complete regression after six months of corticosteroid therapy. This unusual clinical manifestation could help explain the reactive inflammatory nature associated with IMTs.