Imaging Manifestations of Mediastinal Fat Necrosis

Mediastinal fat necrosis (MFN) or epipericardial fat necrosis, as it is commonly referred to in the literature, is a rare self-limiting cause of chest pain of unclear etiology. MFN affects previously healthy individuals who present with acute pleuritic chest pain. Characteristic computed tomography (CT) findings include a fat attenuation lesion with intrinsic and surrounding increased attenuation stranding. There is often associated thickening of the adjacent pericardium and/or pleural effusions. We present two cases of MFN manifesting as ovoid fat attenuation lesions demarcated by a soft tissue attenuation rim with intrinsic and surrounding soft tissue attenuation stranding and review the clinical and pathologic features of these lesions. Knowledge of the clinical presentation of patients with MFN and familiarity with the characteristic imaging findings of these lesions should allow radiologists to prospectively establish the correct diagnosis and suggest conservative management and follow-up. 1. Introduction Mediastinal fat necrosis (MFN) is a rare self-limiting cause of chest pain, with the first reported cases dating back to 1957 [1]. In the current literature, “epipericardial” or “epicardial” fat necrosis is the term used to identify this condition [2–4]. However, as the juxtapericardial mediastinal fat is characteristically affected, we propose that the term MFN is more appropriate given the anatomical location of the disease process. MFN classically affects previously healthy individuals who present with acute pleuritic chest pain that raises concern for an acute cardiopulmonary process including pulmonary thromboembolic and coronary artery diseases [1–12]. We present two cases of MFN and discuss their clinical, pathologic, and imaging findings. In both cases, the affected patients presented with severe chest pain and no associated physical examination findings or specific laboratory abnormalities. The presentation of acute pleuritic chest pain in association with CT findings of an ovoid juxtapericardial fat attenuation lesion with intrinsic and surrounding increased attenuation stranding, thickening of the adjacent pericardium, and resolution on follow-up imaging can be collectively used to establish the diagnosis [2]. Making the correct diagnosis prospectively mitigates unnecessary testing in favor of conservative management. 2. Case Reports Case 1. A 51-year-old man presented with dyspnea and left pleuritic chest pain that radiated to his back. His physical exam and laboratory tests were normal. PA and lateral chest radiographs showed a small