Volume 135, Issue 6, Pages 1673-1678 (June 2009) A 54-Year-Old Woman With Incidentally Discovered Mass on a Chest Radiograph  Feras A. Sawas, MD, Omar Lababede, MD, Moulay A. Meziane, MD, Andrea V. Arrossi, MD  CHEST  Volume 135, Issue 6, Pages 1673-1678 (June 2009) DOI: 10.1378/chest.08-1305 Copyright © 2009 The American College of Chest Physicians Terms and Conditions

Figure 1 Posteroanterior and lateral chest radiographs. The posteroanterior view (top, A) demonstrates a mass in the upper left hemithorax with partially obscured margins (open white arrow). Adjacent rib erosions are present (thin black arrow). On the lateral view (bottom, B), the mass is more subtle and is projecting posteriorly over the spine (open black arrow). CHEST 2009 135, 1673-1678DOI: (10.1378/chest.08-1305) Copyright © 2009 The American College of Chest Physicians Terms and Conditions

Figure 2 Contrast-enhanced axial CT scan image displayed in soft-tissue window setting (top, A) demonstrates heterogeneous soft tissue mass (open white arrow) in the left apex abutting the chest wall with smooth interface with the lung. Contrast enhanced axial CT image displayed in bone window setting (bottom, B) demonstrates underlying rib erosions (arrow). CHEST 2009 135, 1673-1678DOI: (10.1378/chest.08-1305) Copyright © 2009 The American College of Chest Physicians Terms and Conditions

Figure 3 Top, A: hypercellular area composed of spindle cells with indistinct cell borders arranged in short fascicles with focal nuclear palisading (hematoxylin-eosin, original ×20). The inset shows that tumor cells are diffusely and strongly immunoreactive to S-100 protein (immunoperoxidase S-100, original ×20). Bottom, B: hypocellular area composed of spindle cells arranged haphazardly in a loosely textured matrix with delicate collagen fibers (hematoxylin-eosin, original ×20). CHEST 2009 135, 1673-1678DOI: (10.1378/chest.08-1305) Copyright © 2009 The American College of Chest Physicians Terms and Conditions

Figure 4 Diagram showing the different manifestations of extrapulmonary (pleural/chest wall) lesions on a chest radiograph based on their anatomic location. The drawing on the top is a cross-section of the chest with masses in different anatomic locations (locations A to D). The dashed lines represent the direction of the x-ray beams based on a frontal radiograph. The corresponding radiographic appearance of each lesion is shown at the bottom (panels 1 to 4). Based on the curved nature of the chest wall, most extrapulmonary masses, such as mass A, will be oblique in relation to the x-ray beam and will appear radiographically as a mass with an incomplete margin (panel 1). The obliquity of the lesion will cause a portion of the mass-lung interface (the medial) to be tangential to the radiograph, producing a well-defined margin (arrow head). The lateral border is nontangential and blends with the chest wall, causing its shadow to be ill defined. The visibility of an extrapulmonary mass depends to a large extent on whether a portion of the lesion protrudes into the lung or the air surrounding the body. The portion of the mass that is embedded in the chest wall will not be visible unless it has different density from the adjacent soft tissues. Mass B is a small lesion with no intrathoracic/extrathoracic protruding components, internal calcifications, or rib changes. This is usually not visible (panel 2). A mass involving the posterior chest wall, such as C, will be in a plane perpendicular to the x-ray beam (unlike the oblique plane of mass A). The margins of the mass-lung interface are not tangential to the radiograph beam. The resulting radiographic shadow will be subtle density that fades smoothly from its center (without an abrupt transition) and blends with the density of the adjacent chest wall. The entire margin of this mass is ill defined (panel 3). Mass D, which involves the lateral chest wall, is tangential to the x-ray beam. It projects radiographically as a chest wall-based oval density that has well-defined margins with the lung (panel 4). The angle between the mass and the chest wall is often obtuse (ie, tapered) [arrow]. CHEST 2009 135, 1673-1678DOI: (10.1378/chest.08-1305) Copyright © 2009 The American College of Chest Physicians Terms and Conditions