pleural solitary fibrous tumor

PO

Digital case

 JRC:1603 : Localized fibrous tumor of the pleura.

Localized fibrous tumors of the pleura are rare tumors, accounting for less than 5% of all neoplasms involving the pleura.

Although these tumors affect men and women of all ages, the mean age according to Briselli et al. is 51 years. The tumors are composed of haphazardly arranged fascicles of spindle cells, separated by variable amounts of collagen. These tumors originate from submesoepithelial mesenchymal cells, and approximately 80% arise from the visceral pleura. They are not related to asbestos exposure.

Localized fibrous tumors of the pleura are round or oblong, and the margins are circumscribed and sometimes lobulated. These tumors, commonly found in the dependent portions of the thorax, may range from 1 to 39 cm in diameter.

Large tumors usually displace rather than invade adjacent structures. Because of the presence of a vascular pedicle in 30-50% of patients, these tumors may show a change in shape and location with changes in respiration or position.

On unenhanced CT scans, localized fibrous tumors show soft-tissue attenuation. MR images show intermediate to low signal intensity on T1-weighted images and low signal intensity on proton density- and T2-weighted images. On CT and MR images, marked enhancement caused by the rich vascularization is usually seen with the administration of IV contrast material. CT and MR images may show associated cysts and regions of hemorrhage and necrosis. In a study by England et al. tumoral calcifications were seen in 7% of patients and pleural effusions were identified in up to 17% of patients. Rib erosion is rare.

Although approximately half the patients with localized fibrous tumors of the pleura are asymptomatic, cough, chest pain, and dyspnea may be presenting symptoms, especially in patients with large tumors.

Hypertrophic osteoarthropathy was seen in 4-35% of patients, and hypoglycemia was noted in up to 5% of patients according to Ferretti et al. and Briselli et al. .

The fibrous acellular nature of localized fibrous tumors makes diagnosis by transthoracic needle biopsy difficult.

These tumors are usually slow-growing masses, and surgical excision is usually curative.

Local recurrence has been reported in 16% of patients, but malignant transformation is rare.

IHC

 vimentin+
 CD34+
 BCL2+

Molecualr biology

 NAB2-STAT6 gene fusion in solitary fibrous tumor fusing NAB2 and STAT6

Differential diagnosis

 pleural fibrosarcoma
 pleural synovial sarcoma
 MPNST
 sarcomatoid mesothelioma / desmoplastic mesothelioma

• diffuse on Xray, infiltrative,
• often atypia
• mitotic figures

 spindle cell carcinoma

See also

 pleural tumors

References

 Ferretti GR, Chiles C, Choplin RH, Coulomb M. Localized benign fibrous tumors of the pleura. AJR 1997;169:683-686.

 Briselli M, Mark EJ, Dickersin GR. Solitary fibrous tumors of the pleura: eight new cases and review of 360 cases in the literature. Cancer 1981;47:2678-2689

 Lee KS, Im J-G, Choe KO, Kim CJ, Lee BH. CT findings in benign fibrous mesothelioma of the pleura: pathologic correlation in nine patients. AJR 1992;158:983-986

 England DM, Hochholzer L, McCarthy MJ. Localized benign and malignant fibrous tumors of the pleura: a clinicopathologic review of 223 cases. Am J Surg Pathol 1989;13:640-658