Solitary fibrous tumor of the pleura

Last revised by Mostafa El-Feky on 31 Jul 2022

Solitary fibrous tumors of the pleura are rare benign pleural-based tumors that account for <5% of all tumors involving the pleura.

Throughout much of the twentieth century, there was a continual debate about the precise histology of both normal pleura and pleural tumors. The properties of the mesothelial cell itself were controversial, mostly due to its unique expression of both mesenchymal and epithelial attributes.

Gradually, a distinction was recognized between "localized" versus aggressive mesothelial tumors (i.e. "malignant" mesothelioma). The former entity has been variably termed benign mesothelioma, localized fibrous tumor of the pleura, localized mesothelioma, localized fibrous mesothelioma, localized benign fibroma, or submesothelial fibroma 10. Solitary fibrous tumor of the pleura is now the preferred term per the WHO Classification of Tumors of the Lung, Pleura, Thymus and Heart 12.

Usually presents in the 6th to 7th decades. There is no recognized gender predilection. It has an incidence of 2.8 per 100,000 persons 11.

Usually asymptomatic and discovered as an incidental finding on a routine chest radiograph 3. Of those who are symptomatic, the clinical presentation can be with either a cough, chest pain, or shortness of breath. 

Asbestos exposure is not an association 15.

They are composed of irregularly arranged fascicles consisting of spindle cells separated by collagen and are thought to originate from submesothelial mesenchymal cells. Approximately 80% of pleural fibromas arise from the visceral pleura 12. Myxoid or cystic degeneration can occur.

Approximately 30% of solitary fibrous tumors of the pleura are malignant 12

There may be a predilection towards the mid to lower zones of the chest. In ~80% of cases, they arise from visceral pleura, with the remainder arising from the parietal pleura.

  • lipomatous hemangiopericytoma: a fat-forming variant of pleural fibroma 7

Presents as a pleural-based mass, which tends to be relatively circumscribed, but can also be lobulated. It often forms an obtuse angle with the chest wall and may grow to a large size. Pedunculated lesions can change position and appearance with respiration or with a change in position on serial radiographs. 

Calcification, rib destruction, and pleural effusions are typically not associated features.

Tends to have soft tissue attenuation on unenhanced scans and shows relatively homogeneous intense background enhancement on contrast-enhanced scans (from rich vascularization). Non-enhancing areas may be present, corresponding to necrosis, myxoid degeneration, or hemorrhage within the tumor. A pedicular attachment may also be seen. The incomplete border sign may be present in the portion of the mass contiguous with the pleura.

Due to the fibrous component, signal characteristics tend to be:

  • T1: typically low to intermediate signal
  • T2: typically low signal overall (thought to be due to high cellularity and abundant collagen); areas of necrosis and myxoid degeneration can have high signal
  • T1 C+: In general, increased vascularity causes intense enhancement post intravenous gadolinium administration 14

MR may also show necrotic, hemorrhagic, and cystic components in greater detail if these are present.

The majority of tumors tend to be benign and slow-growing. Malignant tumors occur at a rate of ~30% (range 10-57%) 12. Surgical resection is the treatment of choice 5,6; Chemotherapy and radiotherapy are used in the minority (<5%) of patients 12

Malignant solitary fibrous tumors of the pleura can metastasize (in order of frequency) to the pleura, chest/abdominal wall, lung, peritoneum, and/or liver. Metastases to the brain or bone are rare 13

Recurrence rates post-resection are ~12.5% (range 9.9-15%) of malignant tumors and ~3% (range 2-4%) of benign tumors with at least 25% presenting with a first recurrence after 5 years 12. Recurrence rates after re-resection are high (~60%) 12. 5-year survival is ~85% 12

Understanding of primary pleural neoplasia has changed drastically since the late 1800s, and so the associated terminology has also changed. German pathologist Ernst Leberecht Wagner (1829-1888) is generally credited with the first description of pleural mesothelioma / pleural fibroma in 1870, although he described it "tuberkelähnliche" lymphadenome ("tubercle-like" lymphadenoma) 9. Primary pleural malignancies were rare until the twentieth century when incidence increased considerably due to environmental exposures.

Considerations for extremely well-defined lesions include:

If not extremely well defined, consider:

Also, consider the differential for a single pleural mass.

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Cases and figures

  • Figure 1: gross pathology
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  • Case 1
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  • Case 2
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  • Case 3
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  • Case 4
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  • Case 5
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  • Case 6: on FDG PET-CT
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  • Case 7
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  • Case 8
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  • Case 9
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  • Case 10: malignant
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  • Case 11: malignant
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  • Case 12
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