18F-FDG PET/CT in lung B lymphoid hyperplasia-type Castleman disease.

We present a 62-year-old woman who, after a catarrhal episode, underwent a chest xray and a chest CT, identifying a pleural-based mass in the left lower lobe. This lesion presented a mixed pattern with solid and peripheral ground-glass attenuation, and an air-bronchogram sign. Despite de suspicion of bronchopneumonia, a lung neoplasm like a predominantly lepidic adenocarcinoma could not be ruled. A 18 F-FDG PET/CT showed a focal radiotracer uptake with SUVmax of 5.34 in the pulmonary lesion, supporting the neoplastic etiology. Consequently, a lower lobectomy was performed and histological examination concluded that the final diagnosis was a B lymphoid hyperplasia-type Castleman disease. Castleman's disease is an uncommon disorder that can be easily misdiagnosed as lymphoma, neoplasm or infection. Unicentric Castleman's disease (UCD) usually presents a hyaline-vascular histological subtype and is usually asymptomatic. Extranodal involvement is very rare. Only a few cases of solid organ involvement such us spleen or parotid gland have been described. UCD originating in the lung is extremely rare and should be considered in the differential diagnosis of a primary pulmonary malignant tumor.