[Pulmonary undifferentiated carcinoma associated with severe inflammatory response; report of 2 cases].

We present 2 cases with pulmonary undifferentiated carcinoma accompanying severe inflammatory responses. Both patients initially complained high-grade fever. Laboratory data on admission showed leukocytosis and elevation of serum CRP level. In both cases, the tumors were characterized by a low-density mass with the enhanced wall on chest computed tomography (CT). The presence of tumor cells could not be identified by bronchoscopical examination. One patient was suffered from left adrenal metastasis at the diagnosis. Both patients underwent pulmonary resection for the primary tumor. The tumors consisted of marked necrotic tissue and were histologically diagnosed as pulmonary undifferentiated carcinoma cells with sarcomatous elements, which was compatible with pleomorphic carcinoma by new World Health Organization (WHO) classification (1999). After operation, systemic inflammatory response such as high-grade fever, leukocytosis, high level of serum CRP continued and progressed. Furthermore, extrathoracic metastatic lesions newly appeared. Both patients died within 100 days after operation.