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

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

Epidemiology

The is no epidemiologically significant association with asbestos exposure.

Clinical features

The age range of patients is from 5 to 87 with a mean of 50 years. The incidence in men and women is similar. 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; 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.

Macroscopic appearances

60% to 80% of cases arise from the visceral pleura, the remainder from the parietal pleura. Tumours are commonly pedunculated. The cut surface is usually firm, white and has a whorled appearance. Myxoid change, cyst formation, haemorrhage and necrosis are uncommon⁸.

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

• 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

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

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

²Brunnemann, 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.

³Vallat-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.

⁴van 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.

⁵Rossi, 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.

⁶Wang, 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.

⁷Hasegawa, 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.

⁸Graadt 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.

⁹Aubry 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

This page last revised 14.5.2004.

©SMUHT/PW Bishop