Cardiac involvement in systemic sarcoidosis sometimes provokes life-threatening ventricular tachyarrhythmia. Steroid administration is one of the fundamental anti-arrhythmia therapies. For an indication of steroid therapy, a definitive diagnosis of sarcoidosis is required.1) However, cases that are clearly suspected of cardiac sarcoidosis based on their clinical courses sometimes do not meet the current diagnostic criteria and result in the loss of an appropriate opportunity to perform steroid therapy.Here we report a case that was diagnosed as sarcoidosis by incidental biopsy of an inguinal lymph node during cardiac resuscitation for cardiac tamponade.2) While the inguinal lymph node was not swollen on computed tomography, a specimen obtained from an incidental biopsy during the exposure of a femoral vessel for the establishment of extracorporeal cardio-pulmonary resuscitation showed a non-caseating granuloma.This findings suggest a non-swelling lymph node biopsy might be an alternative strategy for the diagnosis for sarcoidosis if other standard strategies do not result in a diagnosis of sarcoidosis.