RESUMEN
INTRODUCTION: Pulmonary complications of radiotherapy are rare, but bronchiolitis obliterans organizing pneumonia (BOOP) is observed in 2.5% of cases. It can develop after radiation treatment of breast cancer as well as, more rarely, lung cancer, sarcoma, Hodgkin's disease or malignant thymoma. CASE: Ten months after radiotherapy for breast cancer, a 52 year-old woman developed migratory alveolar opacities outside the radiation field. Their improvement with corticosteroid treatment led to the diagnosis of BOOP. DISCUSSION: BOOP, which resembles infectious pneumonia, can develop 2-7 months after the end of radiotherapy and is seen especially in women aged 50-60 years with fever and coughs resistant to antibiotics. Dyspnea is far rarer. Imaging reveals patchy infiltrates with widespread bilateral, mobile lesions extended over and above the radiation field. Biopsy is required to confirm diagnosis; sections, which may or may not come from the radiation field, reveal the nonspecific granulomatous alveolar infiltrates typical of BOOP. Other causes should be eliminated (toxic, immune, iatrogenic or even idiopathic infection and recurrent early neoplastic relapse). Association with hormone therapy does not influence the course of BOOP. Outcome with corticosteroid treatment is excellent.