A case of primary malignant fibrous histiocytoma(MFH) of the lung occurring in a 62-year-old man is presented. After preoperative bronchial brushing and washing cytologic diagnosis of poorly differentiated carcinoma, surgical resection and lymph nodes dissection were performed. Subsequent histologic examination revealed a primary MFH. The diagnosis was confirmed by electron microscopic and immunohistochemical examinations. The review of the bronchial brushing and washing cytologic features disclosed many bipolar and a few unipolar spindle tumor cells with a "comet" configuration, mainly single cells, but also forming loose clusters. The nuclei were elongated and hyperchromatic and contained one or more irregular nucleoli. Scattered bizarre, multinucleated tumor giant cells were also present.