A sarcoidosis‐like granuloma reaction in the lymph nodes of a patient with lung squamous cancer: from stasis to the invasive phase with FGFR1 gene amplification

Abstract Background Granulomatous inflammation is considered an immune mechanism against infection or certain non‐neoplastic conditions. Sarcoidosis‐like granuloma reactions ( SGRs ) in primary tumors or in regional lymph nodes are occasionally observed; however, they are rare in lung cancer. Case review In this study, we reported on a case of squamous lung cancer with swollen mediastinal lymph nodes, similar to sarcoidosis. He was misdiagnosed as benign lymph node SGRs or tuberculosis for 2 years. Reexamination of the lymph node by immunohistochemistry confirmed the malignant disease. The lung cancer appeared to remain in the stasis phase for 2 years and then burst to stage IV with the amplification of the fibroblast growth factor receptor 1 gene. Conclusions Although tumor‐induced draining lymph node granulomatous reactions are rare, they did exist in some of the patients. In this case, differential diagnoses with malignant granulomas should be performed carefully to avoid the misdiagnosis of a benign disease. The biological significance of such a granulomatous response in inducing tumor remission or in shielding tumor cells from host lymphocytes remains obscure.