Solitary fibrous tumor (SFT) is a rare mesenchymal neoplasm originating from the visceral pleura. It typically presents as a well-defined, large, hypervascular mass. Most patients are asymptomatic and are diagnosed incidentally. Paraneoplastic syndromes such as hypoglycemia (Doege-Potter syndrome), hypertrophic pulmonary osteoarthropathy (Pierre-Marie syndrome), and digital clubbing may occur in large tumors. 10-20% of tumors show malignant behavior. Nuclear STAT6 expression is the diagnostic immunohistochemical marker.
Age Range
40-70
Peak Age
55
Gender
Equal
Prevalence
Rare
Solitary fibrous tumor originates from submesotelial connective tissue of the pleura (fibroblast-like cells) — not from mesotelial cells. NAB2-STAT6 gene fusion is the pathognomonic molecular feature of SFT and leads to nuclear translocation of STAT6 protein. The tumor's rich vascular structure (feeding artery branching creates a 'staghorn' vascular pattern) forms the basis of intense enhancement on CT. In large tumors, IGF-2 (insulin-like growth factor-2) hypersecretion causes Doege-Potter syndrome (hypoglycemia) — IGF-2 binds to insulin receptors increasing glucose consumption. The pedunculated structure of the tumor results from attachment to visceral pleura by a thin pedicle rather than a broad base, allowing the mass to change position with positional changes.
The combination of very intense heterogeneous enhancement in a pleural-based, well-defined, large mass is the most diagnostic finding combination for SFT. Hypervascular structure (staghorn vascular pattern) forms the basis of enhancement, while the pedunculated structure proves pleural mesenchymal origin. This dual finding combination reliably distinguishes from other pleural-based masses (mesothelioma — does not enhance intensely, round atelectasis — not pedunculated).
Very intense and heterogeneous enhancement on contrast-enhanced CT: the most characteristic CT finding of SFT. Reflects the rich vascular structure of the tumor. Enhancement may be homogeneous (in small tumors) or markedly heterogeneous (in large tumors — due to necrosis, myxoid degeneration, cystic areas). The feeding artery may be seen as enlarged.
Report Sentence
Very intense heterogeneous enhancement is observed in the pleural-based mass on contrast-enhanced series, and solitary fibrous tumor should be primarily considered given the hypervascular character.
Well-defined, smooth-contoured, pleural-based mass: soft tissue density (30-50 HU) on unenhanced CT, usually >5cm in diameter. Acute-angle pleural attachment (not obtuse) is present — this finding indicates pleural origin of the mass. Cystic/necrotic areas may appear as low-density foci.
Report Sentence
A well-defined, smooth-contoured soft tissue mass with acute-angle pleural attachment is identified, suggesting a pleural-origin neoplasm.
Heterogeneous signal on T2 MRI: fibrous component shows low signal (dark), myxoid/cystic areas show high signal (bright). T2 signal heterogeneity is characteristic of SFT and reflects the mixed histological composition of the tumor. Generally intermediate-low signal on T1.
Report Sentence
Markedly heterogeneous signal on T2 MRI is observed in the pleural-based mass with low-signal fibrous and high-signal myxoid/cystic components, consistent with solitary fibrous tumor.
Pedunculated morphology: the mass is attached to the pleural surface by a thin stalk (pedicle). Position change of the mass with patient positioning (mobile mass) is highly characteristic of SFT. Change in mass position on inspiration-expiration or supine-prone CT is a diagnostic clue.
Report Sentence
The mass appears attached to the pleural surface by a thin stalk (pedicle), and this pedunculated morphology is highly characteristic of solitary fibrous tumor.
SFT shows variable FDG uptake on PET-CT: benign forms may show low-moderate FDG uptake (SUVmax 2-5), malignant forms may show high FDG uptake (SUVmax >5). FDG uptake may help assess malignancy potential but is not reliable alone.
Report Sentence
Variable FDG uptake is observed in the pleural-based mass on PET-CT (SUVmax: ...); high uptake levels require correlation with surgical pathology to assess malignant potential.
Criteria
Low mitotic activity (<4 mitoses/10 HPF), no necrosis, low cellularity. 80-90% of all SFTs.
Distinct Features
Well-defined, encapsulated, homogeneous or mildly heterogeneous. Surgical resection is curative — recurrence rate <5%. Paraneoplastic syndromes may also occur in benign form (Doege-Potter). Good prognosis.
Criteria
High mitotic activity (≥4 mitoses/10 HPF), necrosis present, high cellularity, invasive growth, atypia. 10-20% of all SFTs.
Distinct Features
More heterogeneous enhancement, prominent necrotic/cystic areas, margins may be irregular, pleural effusion may accompany. Recurrence rate 30-60%. Metastases (lung, liver, bone) may develop. Adjuvant therapy is controversial — temozolomide/bevacizumab combination regimens are being tried.
Criteria
SFT >15cm in diameter. Marked heterogeneity, necrosis/cystic degeneration areas, and increased paraneoplastic syndrome risk due to large size.
Distinct Features
May occupy a large portion of the hemithorax and cause mediastinal shift. Doege-Potter syndrome (hypoglycemia) occurs in 5% and is more common in large tumors. Compression atelectasis, dyspnea, and chest pain are common symptoms. Preoperative embolization may be considered for bleeding control.
Distinguishing Feature
Round atelectasis shows comet tail sign (curving bronchovascular structures) and volume loss — not present in SFT. Enhancement in round atelectasis is homogeneous and moderate (perfusion of atelectatic parenchyma), while in SFT it is very intense and heterogeneous (hypervascular tumor). Asbestos plaques are associated with round atelectasis, not SFT.
Distinguishing Feature
Lung adenocarcinoma is typically parenchymal, with spiculated margins — not pleural-based. Enhancement is less intense compared to SFT. Does not show pedunculated structure. Air bronchogram and ground-glass halo may be seen in adenocarcinoma but not in SFT.
Distinguishing Feature
Pulmonary lymphoma tends to show diffuse infiltrative pattern, mediastinal lymphadenopathy, and pleural effusion. SFT's intense enhancement and pedunculated morphology are not seen in lymphoma. PET-CT shows intense FDG uptake (SUVmax usually >10) in lymphoma.
Urgency
routineManagement
surgicalBiopsy
NeededFollow-up
6-monthPrimary treatment for solitary fibrous tumor is surgical resection (usually thoracoscopic or via thoracotomy). In benign SFT, complete resection is curative — 5-year recurrence rate <5%. In malignant SFT, recurrence is 30-60% and long-term follow-up (5-10 years) is required — 6-monthly CT controls are recommended. Preoperative embolization in giant tumors may reduce intraoperative bleeding. Doege-Potter syndrome (hypoglycemia) resolves immediately after surgery. Adjuvant therapy in malignant form is not standard, but temozolomide/bevacizumab combination is being studied. Biopsy (CT-guided percutaneous or thoracoscopic) is required for preoperative histological confirmation.
Most SFTs are benign, but malignant transformation may occur. Surgical resection is curative. Prognosis after complete resection is excellent. Large size, necrosis, and mitotic activity are indicators of malignancy.