Inflammatory myofibroblastic tumor on intercostal nerve presenting as paraneoplastic pemphigus with fatal pulmonary involvement

Inflammatory myofibroblastic tumors (IMTs) are benign neoplasms that can occur at different anatomic sites with nonspecific clinical symptoms. A 48-yr-old woman presented with a 2-month history of a relapsed oral ulcer, progressive dyspnea, and a thoracic pain induced by breathing. A tumorous mass was noticed in the right costodiaphragmatic recess on chest computed tomography and magnetic resonance imaging, and the patient underwent a right costotransversectomy with excision of the tumor, which originated from the 12th intercostal nerve. Histology and immunohistochemistry showed that the tumor was an IMT of the intercostal nerve. The patient's postoperative course was not favorable; dyspnea persisted after surgery, and a progressive pulmonary compromise developed. The cause of the respiratory failure was found to be bronchiolitis obliterans, which in this case proved to be a fatal complication of paraneoplastic pemphigus associated with an IMT. This case of IMT of the spinal nerve in the paravertebral region is unique in terms of its location and presentation in combination with paraneoplastic pemphigus, which is rare. A brief review of the heterogeneous theories concerning the pathogenesis, clinicopathological features, and differential diagnosis of this disease entity is presented.