A 60-year-old woman was evaluated for a mass lesion shown on a radiograph of the thorax. The patient had been well until 6 weeks before, when progressive shortness of breath, coughing and left-sided chest pain, and pain between her shoulders developed. Her medical history revealed rheumatoid arthritis for 30 years, for which she received prednisolone, 10 mg/d. In 1994, breast-conserving surgery was performed because of a metaplastic carcinoma of the right breast. After surgery, she received adjuvant radiotherapy. No lymph node metastases were found. During follow-up, no signs of metastasis or relapse were observed. There was no history of smoking.