A 67-yr-old man with a 40-yr history of smoking presented to his family physician with a 2-wk history of productive cough with blood-tinted sputum. No other significant illnesses were noted in his medical history. Physical examination revealed no abnormal findings. Chest roentgenograms showed a 3-cm, wellcircumscribed, intraparenchymal and solitary mass lesion located in his right upper lobe of the lung, suggesting a bronchogenic carcinoma. The lung mass was further confirmed by chest computer tomography (CT) scans; and routine blood work, urinalysis, and urine and sputum cytology detected no abnormalities. Further comprehensive diagnostic imaging studies revealed no extrathoracic tumors. The patient underwent a bronchoscopy with a flexible fiberoptic bronchoscope. An ulcerated tumor located in the right upper lobe bronchus was visualized. Cytologic materials procured by bronchial wash and brush, bronchoalveolar lavage, and tumoral needle aspiration using an 1-cm-long, 22-gauge, Wang-type needle were obtained for cytologic evaluation. A bite biopsy of the bronchial tumor was also performed and a few minute, friable tissue fragments were obtained and processed according to the routine technique for histologic study. Two smears were prepared from the bronchial brush, and four cytospin smears were prepared from each cell sample obtained by bronchial wash and bronchoalveolar lavage. The tumoral needle aspirate was scanty in cellularity. Two direct smears were prepared from the needle aspirate and no cell block was made. The prepared smears were fixed in 95% ethanol and stained by the Papanicolaou method. Only one of the two smears prepared from the bronchial brush showed a few bundles of elongated smooth muscle cells with well-defined, granular cytoplasm and elongated, atypical nuclei (Fig. 1). The tumoral needle aspirate revealed only single, loosely clustered, elongated, slightly pleomorphic, naked, hyperchromatic nuclei with blunt ends (Fig. 2). The cytologic observations found in bronchial brush and needle aspirate were in keeping with those of a well-differentiated leiomyosarcoma. The other cell samples revealed no cancer cells. The bronchial biopsy showed only necrotic material and was nondiagnostic. No immunocytochemical staining was performed on the only one smear containing intact neoplastic smooth muscle cells. Because the patient had no history of a resected leiomyosarcoma and no tumor was detected by clinical and diagnostic imaging studies, a diagnosis of primary lung leiomyosarcoma (PLL) was made.The patient's lung tumor was removed by upper lobectomy. It was oval in shape, well demarcated, nonencapsulated, and measured 3 cm in greatest dimensions. The central part of the tumor was occupied by the superior lobar bronchus, which was extensively destroyed by tumor invasion. The visceral pleura was intact and no enlarged lymph nodes were found in hilum of the resected lobe of the lung. Representative tumor tissue sections were fixed in formalin and processed for histologic and immunohistochemical (IM) studi...