ª Springer Science+Business Media New York 2014
Abdominal Imaging
Abdom Imaging (2014) DOI: 10.1007/s00261-014-0155-4
Imaging findings of solitary fibrous tumor in the abdomen and pelvis T.-T. Tian,1 Jing-Tao Wu,1 X.-H. Hu,1 G.-M. Yang,1 J. Sun,1 W.-X. Chen,1 X.-C. Tian2 1
Department of Radiology, Su Bei People’s Hospital of Yangzhou University, No. 98, Nan Tong West Road, Yangzhou 225009, Jiangsu, People’s Republic of China 2 Department of Pathology, Su Bei People’s Hospital of Yangzhou University, Yangzhou, Jiangsu, People’s Republic of China
Abstract Purpose: The purpose of this study was to investigate the imaging characteristics of solitary fibrous tumor (SFT) in the abdomen and pelvis. Methods: Nine cases of SFT confirmed by surgery and pathology were retrospectively analyzed in terms of computed tomography (CT, eight cases) and magnetic resonance imaging (MRI, one case). Results: SFT were located in the retroperitoneum (4/9), abdominal cavity (1/9), pelvis (4/9). Eight cases were single (8/9) and one case (1/9) with three tumors. The average tumor size of 11 lesions was 9.7 cm (4.7–20 cm). Nine tumors were round or ovoid, and two lesions were irregular. The CT value of the plain scans ranged from 33 to 43 Hounsfield units (HU, mean 37.6 HU) in five cases. Arterial-phase CT found solid parts demonstrate avid enhancement (eight cases) and five of them presented with multiple circuitous vessels along the periphery with a CT value of 68–89 HU (mean 76.6 HU). In the venous and delayed phases, enhancement was strengthened progressively. The CT values at venous (eight cases) and delayed phases (five cases) were 108–115 and 112–123 HU respectively, with averages of 109.8 and 114.8 HU. Patch or nodular no-enhanced areas were observed in eight cases during the enhanced phases. One case showed isointensity on T1-weighted images and high signal intensity on T2weighted images accompanied by linear or curvilinear hypointense lines. Intense enhancements along with linear no-enhancement areas are seen in the arterial and venous phases. Conclusion: The possibility of SFT should be considered when a single or multiple masses with sharp border, inhomogeneous density or signal are detected, especially, with inhomogeneous intense enhancement in the arterial phase being maintained in the venous and delayed phases.
Correspondence to: Jing-Tao Wu; email: [email protected]
Key words: Solitary fibrous tumor—Computed tomography—Magnetic resonance imaging
Solitary fibrous tumor (SFT) was originally described as ‘‘benign fibrous mesothelioma’’ of the pleural cavity and was erroneously thought to be confined to the serosal surfaces. After several decades of controversy, SFT is now regarded as the ubiquitous mesenchymal neoplasm of fibroblastic origin [1, 2]. SFT in the abdomen and pelvis is sporadic and often summarized as case report in the published literature [2–6]. Therefore, most radiologists have a lack of knowledge about SFT, and preoperative diagnosis is often a challenging work. The primary aim of this study was to discuss clinical features, pathologic findings, and imaging manifestations of SFT arising from abdomen and pelvis. A greater awareness of these characteristics will improve the diagnosis accuracy.
Methods and materials Patients An Institutional Review Board exemption and a waiver of the requirement of the written informed consent were obtained to perform this retrospective study. Nine cases of SFT confirmed by surgery and pathology were collected from July 2009 to December 2012. There were five males and four females ranging in age from 21 to 66 years, with a mean age 48.8 years old. Table 1 summarizes the clinical information, including patient age, sex, location of the tumor, as well as the pathological results and clinical follow-up.
Imaging protocols Eight patients underwent enhanced computed tomography (CT) examination: five also with plain CT scans and
T.-T. Tian et al.: Imaging findings of solitary fibrous tumor
T.-T. Tian et al.: Imaging findings of solitary fibrous tumor
A 63-year-old woman complained of upper abdominal pain persisting for several years. A Axial CT nonenhanced scans showed two encapsulated, measuring 12.1 9 9.5, 8.9 9 7.7 cm, masses compressing the liver to the inferior side (white arrows in A). Its solid component showed a CT value of 35 HU. B Axial contrast-enhanced CT showed the two tumors enhanced intensely with serpentine vessels (black arrows in B) along the periphery in the early arterial phase. The CT value of the solid component was about 70 HU. C, D Persistent or prolonged enhancement in the venous and delayed phases correlates with hypercellular areas, whereas mild enhancement in the arterial phase with increasing enhancement in the delayed phase correlates with the fibrous or collagenous stroma. The CT values of the solid components at 60 and 120 s were 108 and 112 HU (white arrows in C, D). E Coronal reconstruction disclosed that there were three tumors that had a severe compression to the neighboring structures (white arrow in E). F The tumor mainly consisted of spindle-shaped cells in short interlacing fascicles with numerous thin-walled blood vessels (H&E stain, 9200). Central hypoenhancing or nonenhancing areas can be seen in the tumor, which represent necrosis or cystic change.
b Fig. 1.
three without. CT examinations were performed on a 64slice spiral CT system (Lightspeed VCT 64; GE Healthcare, Milwaukee, WI). Abdominal and pelvic scan conditions: detector collimation 64 9 0.6 mm, gantry rotation time 0.5 s, pitch 1.4, tube voltage 120 kVp, abdominal reference tube current 230 mAs. Intravenous contrast material (iopromide, Ultravist 320; Schering, Berlin, Germany) was administered at a dose of 2 mL/kg of body weight and at a rate of 3 mL/s to a maximum of 150 mL using a power injector, or at a slower rate (minimum of 2 mL/s) if required when venous access was suboptimal. The contrast agent application was controlled by a bolus-tracking technique. Multiphase scan was administered at 30, 60, and 120 s after injection of contrast agent in five cases, and at 30 and 60 s in three cases. The plain CT scans of the cases are used to find lesions in the abdomen and pelvis, while the aims of contrast-enhanced CT scan are to target tumors. A lead coat was used to protect the sex organs and head in young patients.
One patient underwent magnetic resonance imaging (MRI) using a Siemens scanner Magnetom Trio 1.5T. Before contrast injection, routine pelvic protocol was applied: axial T1-weighted imaging (T1 WI, TR 117 ms, TE 4.76 ms) and T2-weighted imaging (T2 WI, TR 3800 ms, TE 108 ms), and sagittal T2-weighted imaging with fat-suppressed (TR 3600 ms, TE 73 ms)were measured. The following parameters matrix 256 9 256, acquisition time two–four times, slice thickness 5–8 mm, and slice distance 2 mm were used. Gadolinium (Gd)diethylenetriaminepentaacetic acid was administered with a dose of 0.1 mmol/kg of body weight. Axial- and coronal- enhanced scans were administered. The arterial and venous delayed times were 25 s and 50–60 s, respectively, after injection of contrast agent.
Imaging analysis Two experienced abdominal and pelvic radiologists (J-T Wu and W-X Chen 20 years of CT experience and 15 years of MRI experience) were responsible for analysis of CT and MRI images. Findings were analyzed regarding the position, size, shape, density, signal, margins, and enhancement patterns. Consensus was reached after discussion, if disagreement arose between them.
Results Clinical results The clinical and histological findings of the patients are summarized in Table 1. Age ranged between 21 and 66 years, and there were more men than women. The locations of the tumors were as follows: four in the retroperitoneum, one in the abdominal cavity and four in the pelvis (bladder, ovary, prostate, and pelvis, respectively). The size of the lesions ranged between 4.7 and 20 cm. Five tumors were larger than 10 cm in size. Clinically, five cases manifest as a slow-growing mass with abdominal pain, one patient presented with urinary retention, and three patients were asymptomatic. Patients were followed for a duration 2–3 years. Recurrence occurred in one
Table 1. Clinical and histological findings of nine cases Cases 1 2 3 4 5 6 7 8 9
Age (years)
Sex
Tumor location
Tumor number
Size (cm)
Malignant criteria
63 21 31 49 66 65 54 47 30
F F M M M M F M F
Retroperitoneum Retroperitoneum Abdominal cavity Retroperitoneum Bladder Prostate Ovary Retroperitoneum Pelvis
M/3 S S S S S S S S
10.5/9.2/4.7 10.3 20 16.9 7.9 9.8 8 11.7 8.3
No No Yes No No No Yes No No
M male, F female, M multiple, S single
Follow-up (years) 3 2 2.5 2 2 3 2 3 2
Recurrence No No Yes No No No No No No
T.-T. Tian et al.: Imaging findings of solitary fibrous tumor
Fig. 2. SFT of the retroperitoneum in a 49-year-old with lower abdominal pain for 3 years. A Axial contrast-enhanced CT scan shows a large mass measuring 16.9 9 9.2 cm (white arrow in A) in the lower left abdomen. which compresses the small bowel and displaces it to the right side. The mass has heterogeneous enhancement with multiple circuitous feeding vessels (black arrow in A) extending to the center of the tumors in the
arterial phase. The CT value of the solid component was about 80 HU. B The enhancement persists with patch or irregular nonenhanced areas during the venous phase with a maximum CT value of 110 HU (white arrow in B). Surgical excision was performed; the results of histopathologic analysis confirmed the diagnosis of SFT. C, D Immunohistochemical test showing the tumor was positive for CD34 (C), Bcl-2 (D).
patient. This patient experienced recurrence once at the surgical site after the first surgery (case 3).
Pathological criteria for malignancy were evaluated in surgical specimens. Only two cases showed high cellularity, nuclear pleomorphism, and increased mitotic index [>3 mitoses/10 high-power field (HPF)]. Immunohistochemically, seven cases were typically positive for CD34 (Fig. 2c), Bcl-2 (Fig. 2d), and vimentin, CD99; and negative for SMA, S100, and desmin. Two cases were negative for CD34. The histopathologic findings combined with immunohistochemical stains confirmed the identification of SFT.
Surgical and pathological results Eight cases were single (8/9) and one case (1/9) was with three tumors. Eleven lesions were surgically resected. Macroscopically, the margins of the lesions were clear. They were oval, round, or irregular, with a complete capsule. The lesions were of firm mass with a yellow-tan to white whorled and high vascularity appearance of the cut surface (Fig. 3d). Histologically, tumors are composed of juxtaposed hyper- and hypocellular spindle cell proliferation, dense collagenous stroma, and numerous thin-walled blood vessels with a staghorn configuration (Fig. 1f). Nine tumors had irregular areas of necrosis.
Imaging findings The majority of SFTs in our series were single (8/9) except in one case (1/9) with three tumors (Fig. 1a–f). Nine tumors were round or ovoid, and two lesions were
T.-T. Tian et al.: Imaging findings of solitary fibrous tumor
Fig. 3. SFT arising from the retroperitoneum in a 21-yearold woman who presented with intermittent abdominal pain in the last 6 years. A Axial contrast-enhanced CT scan shows a large, well-defined, heterogeneously enhanced mass with several circuitous vessels in the arterial phase (white arrow in A). The maximum CT value was about 83 HU in the arterial
phase. B, C Persistent enhancement (white arrow in B, C) in the venous and delayed phases, findings consistent with an SFT. The CT value at 60 and 120 s were 113 and 123 HU, respectively. D Gross cut specimen of the mass reveals a yellowish white and high vascularity appearance of the cut surface.
irregular. All tumors were sharply demarcated. SFTs located in abdomen and pelvis were large, ranging from 4.7 to 20 cm in diameter (mean = 9.7 cm). All cases showed signs of compression of the surrounding structures, and no cases had evidence of direct tumor invasion to an adjacent structure or the presence of lymphadenopathy.
68–89 HU, with an average of 76.6 HU. Persistent or prolonged enhancements in the venous phases (n = 8) and delayed phases (n = 5) were observed. The CT values at venous and delayed phases were 108–115 and 112–123 HU with average values of 109.8 and 114.8 HU, respectively (Figs. 2b, 3b, c). Eight cases presented with patch or nodular no-enhanced areas during enhanced phases (Fig. 1d). The CT values of plain and multiphase enhanced scans are summarized in Table 2.
At CT. The plain CT scan of five cases (5/8) revealed slightly heterogeneous masses with solid density and nodular, patch low-attenuation. Plain CT values ranged from 33 to 43 HU with an average of 37.6 HU (Fig. 1a). During contrast-enhanced multiphase scans, eight patients showed solid parts demonstrating avid enhancement, and five of them presented with multiple circuitous vessels along the periphery in the arterial phase (Figs. 1b, 2a, 3a). The CT values at 30 s were in the range of
At MRI. The case located in the pelvis showed isointensity to muscle on T1-weighted images and high signal intensity on T2-weighted images. There were many linear or curvilinear hypointense lines on T1- and T2-weighted images. Intense enhancement with linear no-enhancement areas is seen in the arterial and venous phases after administration of Gd contrast material.
T.-T. Tian et al.: Imaging findings of solitary fibrous tumor
Table 2. CT values of eight patients with SFT in the abdomen and pelvis Cases
1 2 3 4 5 6 7 8 Mean
Non-enhanced CT value (HU) 35 41 33 36 43 37.6
Enhancement 30 s (HU)
60 s (HU)
70 80 83 68 83 89 68 72 76.6
108 109 113 106 110 115 108 110 109.8
120 s (HU) 112 116 123 110 116 114.8
HU Hounsfield unit
Discussion SFTs which were first described in 1931 are rare tumors that primarily occurred in the pleural cavity [2]. In recent years, SFTs have been described in various extrapleural sites, such as the mediastinum [3], pericardium, nasal cavity and paranasal sinuses [4], and retroperitoneum [5]. SFTs in the abdomen and pelvis are rare: no more than 100 cases have been reported [6]. Clinically, SFT commonly presents during the fifth and sixth decades of life, and men and women appear to be affected equally [1, 7]. In the current case series, the male/female ratio was 5:4. Most patients are asymptomatic or present with abdominal fullness, abdominal pain, or symptoms related to compression of adjacent structures. Moreover, some cases are diagnosed with hypoglycemia, due to insulin-like growth factor II secreted by the tumor cells of SFTs [8]. Most SFTs have been reported to be benign, and complete surgical resection remains the treatment of choice [1, 6, 9]. In our study, all the patients experienced complete resection, and eight cases (seven benign and one malignant) had a good prognosis after 2–3 years of follow-up. Although most SFTs have been reported to be benign histologically, the behavior of SFTs is unpredictable, and approximately 10–15 % of them show recurrent and/or metastatic disease [1, 10]. One patient in our study experienced recurrence at 13 months after the first complete surgery. Local recurrence of SFT, although rare, is a possibility; therefore, we still highlighted the complete surgical resection and postoperative long-term follow-up. Grossly, SFT appears as a well-circumscribed, firm mass with a yellow-tan to white, whorled appearance of the cut surface. At histopathologic analysis, SFTs are typically composed of juxtaposed hyper- and hypocellular spindle cell proliferation, dense collagenous stroma, and numerous thin-walled blood vessels with a staghorn configuration [11]. Areas of hemorrhage and necrosis can be seen. Other findings found that malignant SFTs are typically large and demonstrate cellular atypia, nuclear pleomorphism, a high number of mitotic figures (more
than 3 mitoses/10 HPFs), and more frequent areas of necrosis and hemorrhage. Two cases diagnosed as malignant SFTs in this study corresponded to these findings [11, 12]. Immunohistochemical studies revealed reactivity for CD34, Bcl-2 and vimentin, with no staining for keratin, S100, or actin, confirming the diagnosis of a SFT. In this study, seven cases were typically positive for CD34, Bcl-2, and vimentin; and negative for SMA, S100, and desmin. Two cases diagnosed as malignant SFTs were negative for CD34. It corresponded to the other findings that malignant SFTs tend to lose CD34 immunoreactivity and overexpress p53 and S100 [11, 12]. At CT imaging, we observed that the density and enhancement patterns of SFTs arising from abdomen and pelvis are related to the cellularity, vascularity, collagen distribution and necrosis or cystic degeneration in histopathologic appearance [1, 13–15]. On nonenhanced CT and SFT manifests solid densities corresponding to cellularity, vascularity, and distribution of collagenous, or fibrous stroma. The areas of necrosis or cystic degeneration show low densities. In our series, seven cases presented with areas of patch low-attenuation. Macroscopically heterogeneous cystic or necrosis density was observed. The imaging appearance, particularly the enhancement pattern on dynamic contrast-enhanced CT images, can vary widely depending on the distribution of cellularity, vascularity, and collagenous or fibrous stroma [13–15]. On contrast-enhanced images, we observed that the heterogeneously enhancing masses are related to the vascularity, cellularity, and collagen distribution. After administration of intravenous contrast material, hypervascular areas enhance intensely with serpentine vessels along the periphery in the early arterial phase. The maximum enhancement value was 89 HU (mean 76.6 HU). The hypercellular areas show moderate enhancement, and areas of necrosis or of cystic or myxoid degeneration are not enhanced. Persistent or prolonged enhancements in the venous and delayed phases correlate with hypercellular areas, whereas mild enhancement in the arterial phase with the increasing enhancement in the delayed phase correlates with the fibrous or collagenous stroma [1, 13–16]. CT values at 60 and 120 s were 108–115 and 112–123 HU respectively with average of 109.8 and 114.8 HU. Multiphase CT scans can cause high radiation dose for patients and influence the health of patients, especially in young people. Therefore, a lead coat is routinely employed to protect these patients in our hospital. In addition, the contrast-enhanced CT scans of five cases with plain CT are performed to target tumors. Indeed, MRI scan does not use radiation and is therefore, the preferred method. However, due to the limited number of cases (only one in this case), more studies and cases are needed for drawing the conclusion that MRI method precedes the CT method for diagnosis of SFT in the abdomen and pelvis. Moreover, in this study, we showed
T.-T. Tian et al.: Imaging findings of solitary fibrous tumor
a small population imaging features of SFTs arising in the abdomen and pelvis. The accuracies of these imaging findings would require in future probably a prospective study to see if these patterns allow for distinction from other tumors such as retroperitoneal sarcoma. Differential diagnosis of SFTs in the abdomen and pelvis region should include other mesenchymal neoplasms like desmoid tumor, malignant fibrous histiocytoma, sarcomas, or neurogenic tumors. Given the rarity of SFT, prospective imaging diagnosis is not possible.
Conclusion SFTs arising from abdomen and pelvis are rare, occurring predominantly in adolescents. During imaging, the possibility of SFT should be considered when a single or multiple masses with sharp border, inhomogeneous density or signal are detected, especially with inhomogeneous intense enhancement in the arterial phase being maintained in the venous and delayed phases. Central nonenhancing areas and serpentine vessels along the periphery can reinforce the diagnosis. Confirmation diagnosis should be based on immunohistochemical analysis. References 1. Shanbhogue AK, Prasad SR, Takahashi N, et al. (2011) Somatic and visceral solitary fibrous tumors in the abdomen and pelvis: cross-sectional imaging spectrum. Radiographics 31:393–408 2. Briselli M, Mark EJ, Dickersin GR (1981) Solitary fibrous tumors of the pleura: eight new cases and review of 360 cases in the literature. Cancer 47:2678–2689
3. Goto Y, Sakurada T, Suzuki I, Nanjo H, Masuda H (1997) A localized fibrous tumor (mesothelioma) in the mediastinum: report of a case. Surg Today 27:871–873 4. Zukerberg LR, Rosenberg AE, Randolph G, Pilch BZ, Goodman ML (1991) Solitary fibrous tumor of the nasal cavity and paranasal sinuses. Am J Surg Pathol 15:126–130 5. Nakatani T, Tamada S, Iwai Y (2002) Solitary fibrous tumor in the retroperitoneum: a case with infiltrative growth. Acta Urol Jpn 48:637–641 6. Ginat DT, Aqiba B, Shweta B, Vikram D (2011) Imaging features of solitary fibrous tumors. AJR 196:488–495 7. Kubota Y, Kawai N, Tozawa K, et al. (2000) SFT of the peritoneum found in the prevesical space. Urol Int 65:53–56 8. Takizawa I, Saito T, Kitamura Y, et al. (2008) Primary solitary fibrous tumor (SFT) in the retroperitoneum. Urol Oncol 26:254–259 9. Weon YC, Kim EY, Kim HJ, et al. (2007) Intracranial solitary fibrous tumors: imaging findings in 6 consecutive patients. AJNR 28:1466–1469 10. Fine SW, McCarthy DM, Chan TY, Epstein JI, Argani P (2006) Malignant solitary fibrous tumor of the kidney: report of a case and comprehensive review of the literature. Arch Pathol Lab Med 130:857–861 11. Ide F, Obara K, Mishima K, Saito I, Kusama K (2005) Ultrastructural spectrum of solitary fibrous tumor: a unique perivascular tumor with alternative lines of differentiation. Virchows Arch 446:646–652 12. Fukunaga M, Naganuma H, Ushigome S, Endo Y, Ishikawa E (1996) Malignant solitary fibrous tumour of the peritoneum. Histopathology 28:463–466 13. Rosado-de-Christenson ML, Abbott GF, McAdams HP, Franks TJ, Galvin JR (2003) Localized fibrous tumors of the pleura. Radiographics 23:759–783 14. Moser T, Nogueira TS, Neuville A, et al. (2005) Delayed enhancement pattern in a localized fibrous tumor of the liver. AJR 184:1578–1580 15. Fuksbrumer MS, Klimstra D, Panicek DM (2000) Solitary fibrous tumor of the liver: imaging findings. AJR 175:1683–1687 16. Cardinale L, Allasia M, Ardissone F, et al. (2006) CT features of solitary fibrous tumour of the pleura: experience in 26 patients. Radiol Med 111:640–650
Abdominal Imaging
Abdom Imaging (2014) DOI: 10.1007/s00261-014-0155-4
Imaging findings of solitary fibrous tumor in the abdomen and pelvis T.-T. Tian,1 Jing-Tao Wu,1 X.-H. Hu,1 G.-M. Yang,1 J. Sun,1 W.-X. Chen,1 X.-C. Tian2 1
Department of Radiology, Su Bei People’s Hospital of Yangzhou University, No. 98, Nan Tong West Road, Yangzhou 225009, Jiangsu, People’s Republic of China 2 Department of Pathology, Su Bei People’s Hospital of Yangzhou University, Yangzhou, Jiangsu, People’s Republic of China
Abstract Purpose: The purpose of this study was to investigate the imaging characteristics of solitary fibrous tumor (SFT) in the abdomen and pelvis. Methods: Nine cases of SFT confirmed by surgery and pathology were retrospectively analyzed in terms of computed tomography (CT, eight cases) and magnetic resonance imaging (MRI, one case). Results: SFT were located in the retroperitoneum (4/9), abdominal cavity (1/9), pelvis (4/9). Eight cases were single (8/9) and one case (1/9) with three tumors. The average tumor size of 11 lesions was 9.7 cm (4.7–20 cm). Nine tumors were round or ovoid, and two lesions were irregular. The CT value of the plain scans ranged from 33 to 43 Hounsfield units (HU, mean 37.6 HU) in five cases. Arterial-phase CT found solid parts demonstrate avid enhancement (eight cases) and five of them presented with multiple circuitous vessels along the periphery with a CT value of 68–89 HU (mean 76.6 HU). In the venous and delayed phases, enhancement was strengthened progressively. The CT values at venous (eight cases) and delayed phases (five cases) were 108–115 and 112–123 HU respectively, with averages of 109.8 and 114.8 HU. Patch or nodular no-enhanced areas were observed in eight cases during the enhanced phases. One case showed isointensity on T1-weighted images and high signal intensity on T2weighted images accompanied by linear or curvilinear hypointense lines. Intense enhancements along with linear no-enhancement areas are seen in the arterial and venous phases. Conclusion: The possibility of SFT should be considered when a single or multiple masses with sharp border, inhomogeneous density or signal are detected, especially, with inhomogeneous intense enhancement in the arterial phase being maintained in the venous and delayed phases.
Correspondence to: Jing-Tao Wu; email: [email protected]
Key words: Solitary fibrous tumor—Computed tomography—Magnetic resonance imaging
Solitary fibrous tumor (SFT) was originally described as ‘‘benign fibrous mesothelioma’’ of the pleural cavity and was erroneously thought to be confined to the serosal surfaces. After several decades of controversy, SFT is now regarded as the ubiquitous mesenchymal neoplasm of fibroblastic origin [1, 2]. SFT in the abdomen and pelvis is sporadic and often summarized as case report in the published literature [2–6]. Therefore, most radiologists have a lack of knowledge about SFT, and preoperative diagnosis is often a challenging work. The primary aim of this study was to discuss clinical features, pathologic findings, and imaging manifestations of SFT arising from abdomen and pelvis. A greater awareness of these characteristics will improve the diagnosis accuracy.
Methods and materials Patients An Institutional Review Board exemption and a waiver of the requirement of the written informed consent were obtained to perform this retrospective study. Nine cases of SFT confirmed by surgery and pathology were collected from July 2009 to December 2012. There were five males and four females ranging in age from 21 to 66 years, with a mean age 48.8 years old. Table 1 summarizes the clinical information, including patient age, sex, location of the tumor, as well as the pathological results and clinical follow-up.
Imaging protocols Eight patients underwent enhanced computed tomography (CT) examination: five also with plain CT scans and
T.-T. Tian et al.: Imaging findings of solitary fibrous tumor
T.-T. Tian et al.: Imaging findings of solitary fibrous tumor
A 63-year-old woman complained of upper abdominal pain persisting for several years. A Axial CT nonenhanced scans showed two encapsulated, measuring 12.1 9 9.5, 8.9 9 7.7 cm, masses compressing the liver to the inferior side (white arrows in A). Its solid component showed a CT value of 35 HU. B Axial contrast-enhanced CT showed the two tumors enhanced intensely with serpentine vessels (black arrows in B) along the periphery in the early arterial phase. The CT value of the solid component was about 70 HU. C, D Persistent or prolonged enhancement in the venous and delayed phases correlates with hypercellular areas, whereas mild enhancement in the arterial phase with increasing enhancement in the delayed phase correlates with the fibrous or collagenous stroma. The CT values of the solid components at 60 and 120 s were 108 and 112 HU (white arrows in C, D). E Coronal reconstruction disclosed that there were three tumors that had a severe compression to the neighboring structures (white arrow in E). F The tumor mainly consisted of spindle-shaped cells in short interlacing fascicles with numerous thin-walled blood vessels (H&E stain, 9200). Central hypoenhancing or nonenhancing areas can be seen in the tumor, which represent necrosis or cystic change.
b Fig. 1.
three without. CT examinations were performed on a 64slice spiral CT system (Lightspeed VCT 64; GE Healthcare, Milwaukee, WI). Abdominal and pelvic scan conditions: detector collimation 64 9 0.6 mm, gantry rotation time 0.5 s, pitch 1.4, tube voltage 120 kVp, abdominal reference tube current 230 mAs. Intravenous contrast material (iopromide, Ultravist 320; Schering, Berlin, Germany) was administered at a dose of 2 mL/kg of body weight and at a rate of 3 mL/s to a maximum of 150 mL using a power injector, or at a slower rate (minimum of 2 mL/s) if required when venous access was suboptimal. The contrast agent application was controlled by a bolus-tracking technique. Multiphase scan was administered at 30, 60, and 120 s after injection of contrast agent in five cases, and at 30 and 60 s in three cases. The plain CT scans of the cases are used to find lesions in the abdomen and pelvis, while the aims of contrast-enhanced CT scan are to target tumors. A lead coat was used to protect the sex organs and head in young patients.
One patient underwent magnetic resonance imaging (MRI) using a Siemens scanner Magnetom Trio 1.5T. Before contrast injection, routine pelvic protocol was applied: axial T1-weighted imaging (T1 WI, TR 117 ms, TE 4.76 ms) and T2-weighted imaging (T2 WI, TR 3800 ms, TE 108 ms), and sagittal T2-weighted imaging with fat-suppressed (TR 3600 ms, TE 73 ms)were measured. The following parameters matrix 256 9 256, acquisition time two–four times, slice thickness 5–8 mm, and slice distance 2 mm were used. Gadolinium (Gd)diethylenetriaminepentaacetic acid was administered with a dose of 0.1 mmol/kg of body weight. Axial- and coronal- enhanced scans were administered. The arterial and venous delayed times were 25 s and 50–60 s, respectively, after injection of contrast agent.
Imaging analysis Two experienced abdominal and pelvic radiologists (J-T Wu and W-X Chen 20 years of CT experience and 15 years of MRI experience) were responsible for analysis of CT and MRI images. Findings were analyzed regarding the position, size, shape, density, signal, margins, and enhancement patterns. Consensus was reached after discussion, if disagreement arose between them.
Results Clinical results The clinical and histological findings of the patients are summarized in Table 1. Age ranged between 21 and 66 years, and there were more men than women. The locations of the tumors were as follows: four in the retroperitoneum, one in the abdominal cavity and four in the pelvis (bladder, ovary, prostate, and pelvis, respectively). The size of the lesions ranged between 4.7 and 20 cm. Five tumors were larger than 10 cm in size. Clinically, five cases manifest as a slow-growing mass with abdominal pain, one patient presented with urinary retention, and three patients were asymptomatic. Patients were followed for a duration 2–3 years. Recurrence occurred in one
Table 1. Clinical and histological findings of nine cases Cases 1 2 3 4 5 6 7 8 9
Age (years)
Sex
Tumor location
Tumor number
Size (cm)
Malignant criteria
63 21 31 49 66 65 54 47 30
F F M M M M F M F
Retroperitoneum Retroperitoneum Abdominal cavity Retroperitoneum Bladder Prostate Ovary Retroperitoneum Pelvis
M/3 S S S S S S S S
10.5/9.2/4.7 10.3 20 16.9 7.9 9.8 8 11.7 8.3
No No Yes No No No Yes No No
M male, F female, M multiple, S single
Follow-up (years) 3 2 2.5 2 2 3 2 3 2
Recurrence No No Yes No No No No No No
T.-T. Tian et al.: Imaging findings of solitary fibrous tumor
Fig. 2. SFT of the retroperitoneum in a 49-year-old with lower abdominal pain for 3 years. A Axial contrast-enhanced CT scan shows a large mass measuring 16.9 9 9.2 cm (white arrow in A) in the lower left abdomen. which compresses the small bowel and displaces it to the right side. The mass has heterogeneous enhancement with multiple circuitous feeding vessels (black arrow in A) extending to the center of the tumors in the
arterial phase. The CT value of the solid component was about 80 HU. B The enhancement persists with patch or irregular nonenhanced areas during the venous phase with a maximum CT value of 110 HU (white arrow in B). Surgical excision was performed; the results of histopathologic analysis confirmed the diagnosis of SFT. C, D Immunohistochemical test showing the tumor was positive for CD34 (C), Bcl-2 (D).
patient. This patient experienced recurrence once at the surgical site after the first surgery (case 3).
Pathological criteria for malignancy were evaluated in surgical specimens. Only two cases showed high cellularity, nuclear pleomorphism, and increased mitotic index [>3 mitoses/10 high-power field (HPF)]. Immunohistochemically, seven cases were typically positive for CD34 (Fig. 2c), Bcl-2 (Fig. 2d), and vimentin, CD99; and negative for SMA, S100, and desmin. Two cases were negative for CD34. The histopathologic findings combined with immunohistochemical stains confirmed the identification of SFT.
Surgical and pathological results Eight cases were single (8/9) and one case (1/9) was with three tumors. Eleven lesions were surgically resected. Macroscopically, the margins of the lesions were clear. They were oval, round, or irregular, with a complete capsule. The lesions were of firm mass with a yellow-tan to white whorled and high vascularity appearance of the cut surface (Fig. 3d). Histologically, tumors are composed of juxtaposed hyper- and hypocellular spindle cell proliferation, dense collagenous stroma, and numerous thin-walled blood vessels with a staghorn configuration (Fig. 1f). Nine tumors had irregular areas of necrosis.
Imaging findings The majority of SFTs in our series were single (8/9) except in one case (1/9) with three tumors (Fig. 1a–f). Nine tumors were round or ovoid, and two lesions were
T.-T. Tian et al.: Imaging findings of solitary fibrous tumor
Fig. 3. SFT arising from the retroperitoneum in a 21-yearold woman who presented with intermittent abdominal pain in the last 6 years. A Axial contrast-enhanced CT scan shows a large, well-defined, heterogeneously enhanced mass with several circuitous vessels in the arterial phase (white arrow in A). The maximum CT value was about 83 HU in the arterial
phase. B, C Persistent enhancement (white arrow in B, C) in the venous and delayed phases, findings consistent with an SFT. The CT value at 60 and 120 s were 113 and 123 HU, respectively. D Gross cut specimen of the mass reveals a yellowish white and high vascularity appearance of the cut surface.
irregular. All tumors were sharply demarcated. SFTs located in abdomen and pelvis were large, ranging from 4.7 to 20 cm in diameter (mean = 9.7 cm). All cases showed signs of compression of the surrounding structures, and no cases had evidence of direct tumor invasion to an adjacent structure or the presence of lymphadenopathy.
68–89 HU, with an average of 76.6 HU. Persistent or prolonged enhancements in the venous phases (n = 8) and delayed phases (n = 5) were observed. The CT values at venous and delayed phases were 108–115 and 112–123 HU with average values of 109.8 and 114.8 HU, respectively (Figs. 2b, 3b, c). Eight cases presented with patch or nodular no-enhanced areas during enhanced phases (Fig. 1d). The CT values of plain and multiphase enhanced scans are summarized in Table 2.
At CT. The plain CT scan of five cases (5/8) revealed slightly heterogeneous masses with solid density and nodular, patch low-attenuation. Plain CT values ranged from 33 to 43 HU with an average of 37.6 HU (Fig. 1a). During contrast-enhanced multiphase scans, eight patients showed solid parts demonstrating avid enhancement, and five of them presented with multiple circuitous vessels along the periphery in the arterial phase (Figs. 1b, 2a, 3a). The CT values at 30 s were in the range of
At MRI. The case located in the pelvis showed isointensity to muscle on T1-weighted images and high signal intensity on T2-weighted images. There were many linear or curvilinear hypointense lines on T1- and T2-weighted images. Intense enhancement with linear no-enhancement areas is seen in the arterial and venous phases after administration of Gd contrast material.
T.-T. Tian et al.: Imaging findings of solitary fibrous tumor
Table 2. CT values of eight patients with SFT in the abdomen and pelvis Cases
1 2 3 4 5 6 7 8 Mean
Non-enhanced CT value (HU) 35 41 33 36 43 37.6
Enhancement 30 s (HU)
60 s (HU)
70 80 83 68 83 89 68 72 76.6
108 109 113 106 110 115 108 110 109.8
120 s (HU) 112 116 123 110 116 114.8
HU Hounsfield unit
Discussion SFTs which were first described in 1931 are rare tumors that primarily occurred in the pleural cavity [2]. In recent years, SFTs have been described in various extrapleural sites, such as the mediastinum [3], pericardium, nasal cavity and paranasal sinuses [4], and retroperitoneum [5]. SFTs in the abdomen and pelvis are rare: no more than 100 cases have been reported [6]. Clinically, SFT commonly presents during the fifth and sixth decades of life, and men and women appear to be affected equally [1, 7]. In the current case series, the male/female ratio was 5:4. Most patients are asymptomatic or present with abdominal fullness, abdominal pain, or symptoms related to compression of adjacent structures. Moreover, some cases are diagnosed with hypoglycemia, due to insulin-like growth factor II secreted by the tumor cells of SFTs [8]. Most SFTs have been reported to be benign, and complete surgical resection remains the treatment of choice [1, 6, 9]. In our study, all the patients experienced complete resection, and eight cases (seven benign and one malignant) had a good prognosis after 2–3 years of follow-up. Although most SFTs have been reported to be benign histologically, the behavior of SFTs is unpredictable, and approximately 10–15 % of them show recurrent and/or metastatic disease [1, 10]. One patient in our study experienced recurrence at 13 months after the first complete surgery. Local recurrence of SFT, although rare, is a possibility; therefore, we still highlighted the complete surgical resection and postoperative long-term follow-up. Grossly, SFT appears as a well-circumscribed, firm mass with a yellow-tan to white, whorled appearance of the cut surface. At histopathologic analysis, SFTs are typically composed of juxtaposed hyper- and hypocellular spindle cell proliferation, dense collagenous stroma, and numerous thin-walled blood vessels with a staghorn configuration [11]. Areas of hemorrhage and necrosis can be seen. Other findings found that malignant SFTs are typically large and demonstrate cellular atypia, nuclear pleomorphism, a high number of mitotic figures (more
than 3 mitoses/10 HPFs), and more frequent areas of necrosis and hemorrhage. Two cases diagnosed as malignant SFTs in this study corresponded to these findings [11, 12]. Immunohistochemical studies revealed reactivity for CD34, Bcl-2 and vimentin, with no staining for keratin, S100, or actin, confirming the diagnosis of a SFT. In this study, seven cases were typically positive for CD34, Bcl-2, and vimentin; and negative for SMA, S100, and desmin. Two cases diagnosed as malignant SFTs were negative for CD34. It corresponded to the other findings that malignant SFTs tend to lose CD34 immunoreactivity and overexpress p53 and S100 [11, 12]. At CT imaging, we observed that the density and enhancement patterns of SFTs arising from abdomen and pelvis are related to the cellularity, vascularity, collagen distribution and necrosis or cystic degeneration in histopathologic appearance [1, 13–15]. On nonenhanced CT and SFT manifests solid densities corresponding to cellularity, vascularity, and distribution of collagenous, or fibrous stroma. The areas of necrosis or cystic degeneration show low densities. In our series, seven cases presented with areas of patch low-attenuation. Macroscopically heterogeneous cystic or necrosis density was observed. The imaging appearance, particularly the enhancement pattern on dynamic contrast-enhanced CT images, can vary widely depending on the distribution of cellularity, vascularity, and collagenous or fibrous stroma [13–15]. On contrast-enhanced images, we observed that the heterogeneously enhancing masses are related to the vascularity, cellularity, and collagen distribution. After administration of intravenous contrast material, hypervascular areas enhance intensely with serpentine vessels along the periphery in the early arterial phase. The maximum enhancement value was 89 HU (mean 76.6 HU). The hypercellular areas show moderate enhancement, and areas of necrosis or of cystic or myxoid degeneration are not enhanced. Persistent or prolonged enhancements in the venous and delayed phases correlate with hypercellular areas, whereas mild enhancement in the arterial phase with the increasing enhancement in the delayed phase correlates with the fibrous or collagenous stroma [1, 13–16]. CT values at 60 and 120 s were 108–115 and 112–123 HU respectively with average of 109.8 and 114.8 HU. Multiphase CT scans can cause high radiation dose for patients and influence the health of patients, especially in young people. Therefore, a lead coat is routinely employed to protect these patients in our hospital. In addition, the contrast-enhanced CT scans of five cases with plain CT are performed to target tumors. Indeed, MRI scan does not use radiation and is therefore, the preferred method. However, due to the limited number of cases (only one in this case), more studies and cases are needed for drawing the conclusion that MRI method precedes the CT method for diagnosis of SFT in the abdomen and pelvis. Moreover, in this study, we showed
T.-T. Tian et al.: Imaging findings of solitary fibrous tumor
a small population imaging features of SFTs arising in the abdomen and pelvis. The accuracies of these imaging findings would require in future probably a prospective study to see if these patterns allow for distinction from other tumors such as retroperitoneal sarcoma. Differential diagnosis of SFTs in the abdomen and pelvis region should include other mesenchymal neoplasms like desmoid tumor, malignant fibrous histiocytoma, sarcomas, or neurogenic tumors. Given the rarity of SFT, prospective imaging diagnosis is not possible.
Conclusion SFTs arising from abdomen and pelvis are rare, occurring predominantly in adolescents. During imaging, the possibility of SFT should be considered when a single or multiple masses with sharp border, inhomogeneous density or signal are detected, especially with inhomogeneous intense enhancement in the arterial phase being maintained in the venous and delayed phases. Central nonenhancing areas and serpentine vessels along the periphery can reinforce the diagnosis. Confirmation diagnosis should be based on immunohistochemical analysis. References 1. Shanbhogue AK, Prasad SR, Takahashi N, et al. (2011) Somatic and visceral solitary fibrous tumors in the abdomen and pelvis: cross-sectional imaging spectrum. Radiographics 31:393–408 2. Briselli M, Mark EJ, Dickersin GR (1981) Solitary fibrous tumors of the pleura: eight new cases and review of 360 cases in the literature. Cancer 47:2678–2689
3. Goto Y, Sakurada T, Suzuki I, Nanjo H, Masuda H (1997) A localized fibrous tumor (mesothelioma) in the mediastinum: report of a case. Surg Today 27:871–873 4. Zukerberg LR, Rosenberg AE, Randolph G, Pilch BZ, Goodman ML (1991) Solitary fibrous tumor of the nasal cavity and paranasal sinuses. Am J Surg Pathol 15:126–130 5. Nakatani T, Tamada S, Iwai Y (2002) Solitary fibrous tumor in the retroperitoneum: a case with infiltrative growth. Acta Urol Jpn 48:637–641 6. Ginat DT, Aqiba B, Shweta B, Vikram D (2011) Imaging features of solitary fibrous tumors. AJR 196:488–495 7. Kubota Y, Kawai N, Tozawa K, et al. (2000) SFT of the peritoneum found in the prevesical space. Urol Int 65:53–56 8. Takizawa I, Saito T, Kitamura Y, et al. (2008) Primary solitary fibrous tumor (SFT) in the retroperitoneum. Urol Oncol 26:254–259 9. Weon YC, Kim EY, Kim HJ, et al. (2007) Intracranial solitary fibrous tumors: imaging findings in 6 consecutive patients. AJNR 28:1466–1469 10. Fine SW, McCarthy DM, Chan TY, Epstein JI, Argani P (2006) Malignant solitary fibrous tumor of the kidney: report of a case and comprehensive review of the literature. Arch Pathol Lab Med 130:857–861 11. Ide F, Obara K, Mishima K, Saito I, Kusama K (2005) Ultrastructural spectrum of solitary fibrous tumor: a unique perivascular tumor with alternative lines of differentiation. Virchows Arch 446:646–652 12. Fukunaga M, Naganuma H, Ushigome S, Endo Y, Ishikawa E (1996) Malignant solitary fibrous tumour of the peritoneum. Histopathology 28:463–466 13. Rosado-de-Christenson ML, Abbott GF, McAdams HP, Franks TJ, Galvin JR (2003) Localized fibrous tumors of the pleura. Radiographics 23:759–783 14. Moser T, Nogueira TS, Neuville A, et al. (2005) Delayed enhancement pattern in a localized fibrous tumor of the liver. AJR 184:1578–1580 15. Fuksbrumer MS, Klimstra D, Panicek DM (2000) Solitary fibrous tumor of the liver: imaging findings. AJR 175:1683–1687 16. Cardinale L, Allasia M, Ardissone F, et al. (2006) CT features of solitary fibrous tumour of the pleura: experience in 26 patients. Radiol Med 111:640–650
