IgG4-related disease: a new challenging diagnosis mimicking lung cancer.

IgG4-related disease (IgG4-RD) is a progressive inflammatory disease that might rarely involve only the lungs. We retrospectively reviewed the preoperative, clinical and surgical features of patients with a pathology highly suggestive or probable diagnosis of IgG4-RD without extra-thoracic involvement. Five patients were selected, 2 were operated on the right side. Positron emission tomography-computed tomography (PET-CT) showed an uptake in all the patients (median 5.5), and 2 patients had an uptake at the thoracic lymph nodes. Two diagnoses were made through a CT-guided needle biopsy, while 3 were determined based on a lung wedge resection. The levels of serum IgG4 were elevated (>1.35 g/dl) in all the patients. Two patients had a highly suggestive diagnosis of IgG4-RD, and 3 patients had a probable diagnosis of IgG4-RD. The differential diagnosis between IgG4-RD and lung malignancies based only on radiological features is challenging and often requires histological confirmation. A careful preoperative workup and a multidisciplinary approach to PET-positive nodules might help to avoid unnecessary major lung resections.