PTE was suspected at this time, but the patient displayed few risk factors for this condition, so an FDG-PET scan was performed to evaluate potential malignancies in other organs. Focal uptake was found only in the left hilum at an identical site to that of the filling defect seen on the CT scan. In addition, a chest CT scan performed 1 month later showed significant enlargement of the lesion, indicating malignant features. At this time, plasma levels of various tumor markers were measured to provide further information regarding the malignancy. Levels of tumor markers were as follows: pro-gastrin-releasing peptide (Pro-GRP), 67.2 pg/mL (normal range, 0 to 46.0 pg/mL); neuron-specific enolase (NSE), 13.03 ng/mL (normal range, 0 to 10 ng/mL); and carcinoembryonic antigen, 10.3 ng/mL (normal range, 1.0 to 6.5 ng/mL). Bronchofibroscopy revealed extrinsic compression of the posterior wall of the left lower bronchus. A cytologic examination of transbronchial brush specimens from the lesion surface showed no malignancy, while an examination of transbronchial needle aspiration (TBNA) specimens revealed small tumor cells with scant cytoplasm, finely granular nuclei, and inconspicuous nucleoli, indicating small cell carcinoma (Fig 2
, top, A).4 Cell block sections of tumor cells stained positive for cytokeratin (Fig 2, bottom, B) and thyroid transcription factor-1, while negative results were obtained for vimentin, leukocyte common antigen, synaptophysin, and chromogranin. Since no distant metastatic lesions were identified, the small cell carcinoma of the lung was considered to represent limited disease.