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Benign but Not Harmless: Solitary Fibrous Tumor

A chest x-ray study revealed a large mass. (A) The tumor abutted the right diaphragm in this posterior-anterior view. (B) A lateral view shows the same.

A chest x-ray study revealed a large mass. (A) The tumor abutted the right diaphragm in this posterior-anterior view. (B) A lateral view shows the same.

For one unfortunate patient, benign histopathology did not lead to a good outcome. A 74-year-old woman presented with dyspnea on exertion and altered mental status. She had no history of lung disease and denied other cardiopulmonary, abdominal, or constitutional symptoms. Her past medical history, besides many years of tobacco abuse, was unremarkable

Assessment

While the patient did not appear to be in respiratory distress, a physical examination revealed hypoxemia on room air, with an initial oxygen saturation of 86%. Percussion of the right lower and middle fields produced stony dull sounds, and breath sounds were absent in these areas. Mild wheezing accompanied by prolonged expiration was audible in all lung fields on the left side. Arterial blood gas demonstrated chronic respiratory acidosis and hypoxemia.

A radiograph of the chest showed a large opacity occupying the right mid to lower thorax (Figure 1). Computed tomography (Figure 2) identified a giant 18 cm × 13 cm × 15 cm mass in the right hemithorax. The growth appeared to compress the right middle lobe and restrict expansion of the right upper and lower lobes. No infiltrates, effusion, or evidence of metastases were seen. A computed tomography-guided biopsy was performed to investigate the suspected neoplastic process (Figure 3). No complications occurred.

Diagnosis

The pathology study classified the mass as a solitary fibrous tumor, a diagnosis confirmed by CD34-positive staining (Figure 4). These rare primary tumors of the pleura originate from the mesenchymal layer.12345Overall, primary tumors of the pleura can be diffuse or localized.5 Diffuse pleural neoplasms arise from mesothelial cells, are associated with asbestos exposure, and have a highly malignant potential, while localized neoplasms, termed solitary fibrous tumors, arise from the submesothelial layer and tend to follow a more benign course; 10%-20% are malignant.123 More than 50% of benign solitary fibrous tumors are asymptomatic, but others can manifest with intrathoracic or constitutional symptoms.2 Our patient’s case appears to be the first reported solitary fibrous tumor diagnosed within the Veterans Health Administration. It reminds us to consider benign pleural tumors in the differential diagnosis of lung masses.

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-Jason Chertoff, MD, MPH, Azka Ali, MD, Brandon Dyer, MD, James Wynne, MD

This article originally appeared in the April 2017 issue of The American Journal of Medicine.

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