We describe a 67-year-old man with severe rheumatoid arthritis of long duration. He developed a peculiar extraarticular rheumatoid complication consisting of localized lung consolidation with a pathological costal fracture, together with an abrupt systemic reaction that occurred in the course of immunosuppressive treatment. The diagnosis first proposed was lung cancer with costal metastases. However exhaustive studies performed in the search of malignancy were systematically negative and pathologic studies finally demonstrated bronchiolitis obliterans with organizing pneumonia (BOOP) as responsible for parenchymal lung consolidation with a rheumatoid nodule eroding bone at the level of the rib fracture. These findings, after long followup of the patient, attest to the rheumatoid origin of his bizarre manifestations and definitely rule out a neoplastic etiology.