Solitary (localised) fibrous tumour (of the pleura), SFT

(Also known by various permutations of benign / localised /solitary / fibrous / pleural/submesothelial mesothelioma / fibroma)

Synonyms

Submesothelial fibroma, localised mesothelioma, fibrous mesothelioma, benign mesothelioma. Most tumours of the pleura previously designated as haemangiopericytoma would now be now considered to be solitary fibrous tumours.

Epidemiology

This is the most common benign neoplasm of the pleura. The is no epidemiologically significant association with asbestos exposure.

Clinical features

The age range of patients is wide, including children, with a mean of 50 years. The incidence in men and women is similar¹⁰. Half of all patients are asymptomatic; others present with cough, chest pain and dyspnea. Malignant tumours may produce haemoptysis. Up to 20% of patients have hypertrophic osteoarthropathy. 5% of patients suffer from hypoglycaemia (Doege-Potter syndrome); most commonly these patients are women.

Although most such tumours occur in the pleura, they have also been reported from a large range of extra-pleural sites.

Radiology

Imaging shows a well defined pleural-based mass.

Macroscopic appearances

60% to 80% of cases arise from the visceral pleura, the remainder from the parietal pleura. Half of these tumours are pedunculated¹⁰. The cut surface is usually firm, white and has a whorled appearance. Myxoid change, cyst formation, haemorrhage and necrosis are uncommon⁸. Rarely, patients have multiple tumours¹⁰.

Histopathology

Commonly described showing a "patternless pattern", as diffuse sclerosis and solid spindle-cell patterns. Cellularity varies, usually with hypocellular areas of "keloid" hyalinisation⁸. Amianthoid stellate areas of collagen deposition may occur⁸. The vasculature has a haemangiopericytomatous pattern⁸. Myxoid change and calcification may be present focally. Osseous and chondroid metaplasia have not been reported⁸. May resemble haemangiopericytoma or nerve sheath tumour.

About 20% of SFT are malignant. Criteria are:

• greater cellularity³

• infiltrative growth pattern

• nuclear variation³

• prominent nucleoli

• more than 4 mitoses per 10 HPFs³

• necrosis³

• (Occasional bizarre cells may be a degenerative feature.)

Immunohistochemistry

Summating results from various papers, positivity is seen in¹:

	pleural	extra-pleural
CD34 (My10 may be more sensitive than QBEND108)	92% (196/213), 10/109	95% (78/82)
bcl-2	96% (81/84)	96% (72/75)
CD99	10/11, 8/109	31/31
CD10	5/5 (3/5: strong and diffuse, 2/5 focal)5
vimentin	91% (170/186)	19/192
NSE	36% (10/28)
muscle-specific actin	18% (12/66)
desmin	12% (20/168): staining is focal
SMA	4% (5/132): staining is focal
S-100	1% (1/107)
cytokeratin	2% ( 4/248)	0/192
EMA	negative8
Calretinin	negative8
neurofilament	0% (0/33)

No positive staining has been reported for factor VIII-related antigen, EMA, CEA, alpha-1-antitrypsin or calretinin

Differential diagnosis: see the immunohistochemistry of the differential diagnosis of spindle cell tumours of the pleura.

• inflammatory / fibrotic process

• desmoid tumour of the pleura

• sarcomatoid / desmoplastic mesothelioma

• monophasic synovial sarcoma: commonly positive for bcl-2 but are negative for CD34

• haemangiopericytoma, including lipomatous haemangiopericytoma⁷

• neurofibroma: may be positive for CD34 and bcl-2 but will also be positive for S-100

• spindle cell lipoma7: also CD34 positive

• dendritic fibromyxolipoma⁷

• cellular angiofibroma⁷

• smooth muscle tumours

  sarcomatoid carcinoma

• Type A thymoma

Prognosis

Resectability is the single most important factor. Pedunculated tumours are likely to have a good outcome, even if showing cellular atypia. Bland tumours may recur.

References

^*1 Ordonez NG. Localized (solitary) fibrous tumor of the pleura. Adv Anat Pathol 2000;7:327-340.

² Brunnemann, R. B., Ro, J. Y., Ordonez, N. G., Mooney, J., El-Naggar, A. K., Ayala, A. G. Extrapleural solitary fibrous tumor: a clinicopathologic study of 24 cases. Mod Pathol 1999;12:1034-42.

³ Vallat-Decouvelaere, A. V., Dry, S. M., Fletcher, C. D. Atypical and malignant solitary fibrous tumors in extrathoracic locations: evidence of their comparability to intra-thoracic tumors. Am J Surg Pathol 1998;22:1501-11.

⁴ van de Rijn, M., Lombard, C. M., Rouse, R. V. Expression of CD34 by solitary fibrous tumors of the pleura, mediastinum, and lung. Am J Surg Pathol 1994;18:814-20.

⁵ Rossi, G., Cavazza, A., Longo, L. and Maiorana, A. Localized pleural metastatic adenosarcoma of the uterine cervix mimicking a malignant solitary fibrous tumour: CD10 has no value in differential diagnosis. Histopathology 2002;41:82-3.

⁶ Wang, J., L. M. Weiss, et al. (2004). "Usefulness of immunohistochemistry in delineating renal spindle cell tumours. A retrospective study of 31 cases." Histopathology 44(5): 462-71.

⁷ Hasegawa, T., Matsuno, Y., Shimoda, T., Hasegawa, F., Sano, T., Hirohashi, S. Extrathoracic solitary fibrous tumors: their histological variability and potentially aggressive behavior. Hum Pathol 1999;30:1464-73.

⁸ Graadt van Roggen JF, Hogendoorn PCW. Solitary fibrous tumour: the emerging clinicopathologic spectrum of an entity and its differential diagnosis. Current Diagnostic Pathology 2004;10:229-235.

⁹ Aubry MC, Bridge JA, Wickert R,Tazelaar HD Primary monophasic synovial sarcoma of the pleura: five cases confirmed by the presence of SYT-SSX fusion transcript. Am J Surg Pathol 2001; 25:776-81

¹⁰ Granville L, Laga AC, Allen TC, et al. Review and update of uncommon primary pleural tumors: a practical approach to diagnosis. Arch Pathol Lab Med 2005; 129:1428-43

This page last revised 8.8.2006.

©SMUHT/PW Bishop