[Langerhans cell histiocytosis of the rib in adult male].

A 57-year-old man was admitted to our hospital with an abnormal shadow on chest X-ray film. Computed tomography (CT) scanning demonstrated a low-density, destructive mass on the right 8th rib. The maximum standardized uptake value of the tumor measured by positron emission tomography (PET) was 2.9, indicating malignancy. Wide resection of the tumor, including the right 8th rib and the 7th to 8th intercostal muscle, was performed. Chest wall reconstruction was achieved with Composix Mesh. The histologic findings revealed proliferation of histiocytes and eosinophil infiltration. No malignant cells were detected in the tumor. Histiocytes stained for S-100 protein and CD1a, compatible with a diagnosis of Langerhans cell histiocytosis (LCH). LCH in the ribs is very rare and difficult to diagnose using CT or PET. Tumor biopsy or resection is needed to diagnose LCH.