Benign Histiocytoma of the Lung: A Case Report

ABSTRACT

Histiocytomas have rarely been reported in the lungs. We report an unusual benign pulmonary histiocytoma in a 45-year-old man and discuss the differential diagnosis. Chest CT showed a well-defined solitary pulmonary nodule of approximately 3 cm in size in the posterobasal segment of the right lower lobe. Posterolateral thoracotomy and wedge resection was performed. Gross examination revealed a mass, measuring 2.2 x 2.1 cm that had a circumscribed margin within the lung parenchyma. Microscopically, the tumor was entirely composed of large polygonal to round cells with a few chronic inflammatory cells. These tumor cells contained abundant cytoplasm which was either granular, eosinophilic or foamy. Immunohistochemically, these cells were diffusely positive for CD68 and focally positive for 1-antitrypsin, but negative for cytokeratin, vimentin, and smooth muscle actin.