Solitary fibrous tumors (SFT) are a rare neoplasm of mesenchymal origin that comprise less than 2% of all soft tissue tumors. The majority are benign, although up to 20% may be malignant.
For a discussion of specific presentations of SFT, please refer to
- solitary fibrous tumor of the pleura
- solitary fibrous tumor of the spinal cord
- solitary fibrous tumor of the dura
Intrathoracic SFT usually presents in the 6th to 7th decades. Extrathoracic SFT occurs in men and women of all ages equally 7.
Although typically asymptomatic, it may present with symptoms and signs related to extrinsic compression of adjacent organs. Rarely solitary fibrous tumors result in non-islet cell tumor hypoglycemia (NICTH) as a result of secretion of insulin-like growth factor-2 (IGF-2) 4-7,11. Rarer still is acromegaly 11.
The majority of solitary fibrous tumors occur in an intrathoracic location but up to one third may occur in extrathoracic locations, and as such they may be encountered essentially anywhere, including 7:
- spinal cord 2-3
- head and neck
- abdominal parenchymal organs
- pelvic organs
SFT most likely arises from submesothelial fibroblasts and used to be included in hemangiopericytoma spectrum 10.
At histology, a collagenous matrix with arrays of spindle cells is usually seen. Areas of necrosis, cystic or myxoid change, calcification, hemorrhage, increased vascularity, atypia, or malignancy may also be seen 7-8.
Immunohistochemical analysis can play an important role in the diagnosis and management 12:
- ~75% of benign solitary fibrous tumors of the thorax stain for CD34, a marker for normal endothelium and vascular tumors
- B-cell lymphoma 2 protein (Bcl-2), a marker of terminal differentiation, and vimentin are also positive in the majority of benign solitary fibrous tumors
- cytokeratin, S-100, and p53 proteins have shown increased expression in malignant solitary fibrous tumors
CT reveals a well-circumscribed, smooth, lobulated soft tissue mass that may contain scattered calcifications. Smaller tumors tend to enhance homogeneously, whereas larger lesions may have central tubular or rounded low-attenuation areas due to cystic or necrotic change.
On MRI, benign solitary fibrous tumors usually has relatively homogeneous low-to-intermediate signal intensity relative to skeletal muscle on both T1-weighted imaging and T2-weighted imaging because of fibrous tissue, as well as intense enhancement.
In addition, there may be areas of subacute hemorrhage that have high T1-weighted signal intensity, as well as non-enhancing cystic or necrotic foci that are more heterogeneous and higher in T2-weighted signal intensity relative to the remainder of the tumor.
However, when a central focus of heterogeneity and variable contrast enhancement is identified in an SFT at CT or MRI, malignant degeneration should be considered 7.
Treatment and prognosis
- benign SFT <10 cm in size typically has a favorable outcome with surgical resection alone
- SFT >10 cm that also harbors malignant foci, and has positive surgical margins tends to have a poor prognosis despite surgical treatment
- optimal adjuvant therapy for this group is unknown, and close-interval follow-up is advised because there is an increased incidence of local recurrence
- 1. Vallat-decouvelaere AV, Dry SM, Fletcher CD. Atypical and malignant solitary fibrous tumors in extrathoracic locations: evidence of their comparability to intra-thoracic tumors. Am. J. Surg. Pathol. 1998;22 (12): 1501-11. Am. J. Surg. Pathol. (link) - Pubmed citation
- 2. Ogungbo B, Prakash S, Kulkarni G et-al. Cervical intra-/extramedullary solitary fibrous tumour. Br J Neurosurg. 2005;19 (3): 254-7. doi:10.1080/02688690500208528 - Pubmed citation
- 3. Metellus P, Bouvier C, Guyotat J et-al. Solitary fibrous tumors of the central nervous system: clinicopathological and therapeutic considerations of 18 cases. Neurosurgery. 2007;60 (4): 715-22. doi:10.1227/01.NEU.0000255418.93678.AD - Pubmed citation
- 4. Suter M, Gebhard S, Boumghar M et-al. Localized fibrous tumours of the pleura: 15 new cases and review of the literature. Eur J Cardiothorac Surg. 1998;14 (5): 453-9. Eur J Cardiothorac Surg (link) - Pubmed citation
- 5. Lee KS, Im JG, Choe KO et-al. CT findings in benign fibrous mesothelioma of the pleura: pathologic correlation in nine patients. AJR Am J Roentgenol. 1992;158 (5): 983-6. AJR Am J Roentgenol (abstract) - Pubmed citation
- 7. Haaga JR, Boll D. CT and MRI of the whole body. Mosby. (2009) ISBN:0323053750. Read it at Google Books - Find it at Amazon
- 8. Robbins SL, Kumar V, Abbas AK et-al. Robbins and Cotran Pathologic Basis of Disease. W.B. Saunders Company. (2010) ISBN:1416031219. Read it at Google Books - Find it at Amazon
- 9. Dähnert WF. Radiology Review Manual. Lippincott Williams & Wilkins. (2011) ISBN:1609139437. Read it at Google Books - Find it at Amazon
- 10. Gengler C, Guillou L. Solitary fibrous tumour and haemangiopericytoma: evolution of a concept. Histopathology. 2006;48 (1): 63-74. doi:10.1111/j.1365-2559.2005.02290.x - Pubmed citation
- 11. Khowaja A, Johnson-Rabbett B, Bantle J et-al. Hypoglycemia mediated by paraneoplastic production of Insulin like growth factor-2 from a malignant renal solitary fibrous tumor - clinical case and literature review. BMC Endocr Disord.14 (1): 49. doi:10.1186/1472-6823-14-49 - Free text at pubmed - Pubmed citation
- 12. Chick JF, Chauhan NR, Madan R. Solitary fibrous tumors of the thorax: nomenclature, epidemiology, radiologic and pathologic findings, differential diagnoses, and management. AJR. American journal of roentgenology. 200 (3): W238-48. doi:10.2214/AJR.11.8430 - Pubmed