Computed Tomographic Scans at Level of Nodule
(A = soft tissue window; B = lung window): A 2.8 x 2 cm smoothly-marginated mass of muscle attenuation is located between the right pericardium, the diaphragm (seen on cut below), and the major fissure (arrow in B). The lesion cannot be entirely separated from the lung. Images with intravenous contrast showed mild enhancement of the mass. Note that the pleura between the spine and left posterior rib demonstrates a small high density plaque consistent with prior asbestos exposure (arrow).
The differential diagnosis is narrowed by this information. The absence of fat in the nodule excludes a pericardial fat pad and pleural lipoma. Contiguity of the diaphragm excludes a foramen of Morgagni hernia. Pericardial cysts and pleural "pseudotumors" are usually water attenuation and show no contrast enhancement. Although ~20% of thymomas may occur in the pericardiac region, contact with the diaphragm is unusual. The clinical data exclude endometriosis (in this man), splenosis, pleural fibrin body (no history of prior trauma or thoracic surgery), pleural lymphoma, and juxtaphrenic lymphadenopathy (usually a prior history or other evidence of disease). Pleural metastases and malignant mesothelioma generally have associated pleural fluid, although evidence of prior asbestos exposure raises the possibility of an atypical presentation of mesothelioma.
Solitary fibrous tumor of the mesothelium and a pulmonary parenchymal nodule such as a primary or metastatic cancer remain possibilities. Although the appearance is extremely unusual for pulmonary sequestration (which is generally posterior and left lower lobe), the important surgical implications of an associated abdominal systemic blood supply prompted an MR angiogram which excluded this possibililty.
1. Wilson AG. Pleura and pleural disorders. In: P Armstrong, AG Wilson, P Dee, DM Hansell (eds): Imaging of Diseases of the Chest, 2nd ed. St. Louis, Mosby-Year Book, 1996, pp. 641-716.
2. Armstrong P. Mediastinal and hilar disorders. In: P Armstrong, AG Wilson, P Dee, DM Hansell (eds): Imaging of Diseases of the Chest, 2nd ed. St. Louis, Mosby-Year Book, 1996, pp. 717-816.
3. Armstrong P. Neoplasms of the lungs, airways, and pleura. In: P Armstrong, AG Wilson, P Dee, DM Hansell (eds): Imaging of Diseases of the Chest, 2nd ed. St. Louis, Mosby-Year Book, 1996, pp. 272-368.
4. Reed JC. Chest Radiology Patterns and Differential Diagnoses. Chicago, Year Book Medical Publisher, 1981, p.59.
Clinical summary Image 1
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