E1250. Varying Appearances of Normal Thoracic Fat: A Pictorial Essay
  1. Janki Patel; Mount Sinai Hospital
  2. Arielle Sasson; Mount Sinai Hospital
  3. Corey Eber; Mount Sinai Hospital
Thoracic fat comes in various shapes, sizes, and distribution and can often be mistaken for pathology. New literature on this topic has not been published for several decades; therefore, younger radiologists may not be as familiar. When interpreting plain radiographs, this knowledge is essential to avoid misinterpreting normal anatomic variations with pathology that may require medical or surgical intervention.

Educational Goals / Teaching Points
The objective of this review is to discuss the manifestations of normal thoracic fat on imaging and common pathologic abnormalities with which they may be confused. Participants will become more familiar with thoracic anatomy. They will also be less likely to overcall normal radiographic findings as pathological concerns.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
The presentation reviews striking manifestations of normal thoracic fat on imaging as follows. Pronounced pericardial fat often surrounds the lower heart borders (more commonly on the left), resulting in a characteristic appearance in the anterior cardiophrenic sulcus. This may obscure the adjacent heart border and simulate a pericardial cyst, lymph nodes, or adjacent parenchymal disease in the lingula or right middle lobe. Apical fat can be falsely interpreted as apical fibrosis or, when convex, could be concerning for masses. Extrapleural fat by the first and second ribs can sometimes be focal and convex, which may be confused with a mass. Extrapleural fat laterally may be confused with pleural effusion. Pericardial fat can be seen invaginating into the major fissure on chest radiographs and mimicking pleural fluid or scarring. Subcostal fat may be mistaken for pleural effusions or scarring laterally or subpleural fibrosis in the apices.

Developing an understanding of the various manifestations of normal thoracic fat is important. This may decrease overcalling pathology on plain radiographs, especially when comparison to prior CT scans are available.