Primary malignant ependymoma of the lung.

In a 64-year-old woman, a solitary pulmonary nodule developed 30 months after combination chemotherapy and thoracic irradiation had been administered for small-cell carcinoma of the ipsilateral lung. No evidence of extrapulmonary tumor was identified, and the nodule was excised. The well-circumscribed tumor had histologic features of a malignant ependymoma. Immunohistochemical staining showed strong reactivity for glial fibrillary acidic protein; staining for S-100 protein, Leu-7, and vimentin was less intense. Focal reactivity for epithelial membrane antigen was also present. Stains for keratin, synaptophysin, and chromogranin were negative. Electron microscopy showed cohesive cells, the cytoplasm of which contained intermediate filaments. Rare well-formed junctions were also noted. Flow cytometry of formalin-fixed paraffin-embedded tissue demonstrated DNA aneuploidy. Six months after the ependymoma was diagnosed, the patient, who had a history of hypertension, died of an intracerebral hemorrhage.