[A case of large cell carcinoma of the lung associated with a sarcoid-like reaction inside the tumor].

A sarcoid-like reaction may occur inside a malignant tumor, in regional lymph-nodes or in adjacent tissues. An 83 year-old man who was found to have a mass in his left lower lung field on a chest radiograph. Transbronchial biopsy was performed and a non-caseating granulomatous lesion caused by a possible infectious disease was diagnosed. However, the size of the mass increased after 6 months. The patient was referred to our hospital, and lung biopsy under video-assisted thoracoscopic surgery (VATS) was performed. Since the initial intraoperative pathologic examination showed the presence of non-caseating epithelioid cell granulomas, only partial resection was conducted. However, detailed postoperative histopathological evaluation led to a diagnosis of large cell carcinoma of the lung associated with an internal sarcoid-like reaction. The patient then received another VATS for left lower lobectomy. Formation of epithelioid cell granulomas within a tumor is quite rare. In cases in which the pathological findings of TBLB specimens do not agree with the clinical course, more thorough approaches such as biopsy under VATS may be required.