Multicentric oncocytoma of the lung diagnosed by fine-needle aspiration

A 50-yr-old man presented with dyspnea. On chest X-ray, multiple pulmonary nodules were observed. Fine-needle aspiration biopsy (FNAB) showed tridimensional aggregates of atypical round epithelial cells, containing numerous cytoplasmic granules. The tissue fragment confirmed the presence of an epithelial tumor composed of trabecular sheets of clear cells, with numerous cytoplasmic granules which stained with phosphotungstic acid hematoxylin (PTAH). Immunohistochemically, the tumor cells were positive for cytokeratins and antimitochondrial antigen, whereas chromogranin, synaptophysin, S-100 protein, and HMB-45 were negative. Clinical and tomographic studies ruled out any tumor mass elsewhere. The rarity of this lesion in the lung and the potential difficulties for its diagnosis prompted us to report the clinical, cytological, and immunohistochemical findings in this case.