[A necrobiotic nodule indistinguishable from lung adenocarcinoma]

A 43-year-old woman was referred for examination because of an abnormal shadow on a chest X-ray film. She had a 12-year history of seropositive rheumatoid arthritis. Chest X-ray films and CT scans showed a pleurabased solitary nodule without a cavity. Cytological examination of a transbronchial biopsy specimen did not lead to a diagnosis, so thoracoscopic enucleation was performed. Histologically, the nodule consisted of lymphocytes and fibroblasts surrounding a central necrotic area, which indicated that it was a rheumatoid nodule. This solitary necrobiotic nodule was radiographically indistinguishable from lung adenocarcinoma, so histologic confirmation was necessary.