Pulmonary inflammatory myofibroblastic tumor (inflammatory pseudotumor, plasma cell granuloma) was reported most often as a single peripheral mass, successfully cured by surgery. A 14-year-old girl presented with a large left pulmonary mass involving and obliterating the main bronchus; there were angioinvasion and infiltration of mediastinum, hilar lymph nodes and pleura. Multiple, often tiny nodules were seen in the right lung. At microscopic examination, there were lymphocytic and plasmacytic infiltrates and borderline myofibroblastic proliferation with focal nuclear anaplasia. Smaller lesions were similar to organizing pneumonia. Disease was progressive in the remaining right lung after surgical resection and a two-month treatment with corticoids. The patient was then treated with chemotherapy. She was alive and well (twenty-month follow-up).