Yonago Acta medica 2005;48:75–81

Solitary Fibrous Tumor of the Buccal Mucosa: A Patient
ReportKazuhiko Tanio, Kazuo Ryoke, Isamu Kodani, Rieko Doi, Yoshiyuki Tanji, Kazuhito
Tohashi and Takayuki Ikeda*
Division of Oral and Maxillofacial Biopathological Surgery, Department of Medicine of Sensory and Motor Organs, School of Medicine, Tottori University Faculty of Medicine, Yonago
683-8504 and *Clinic of Dentistry and Oral Surgery, Tottori Prefectural Central Hospital,Tottori 680-0901 Japan
Solitary fibrous tumor (SFT) is a soft tissue tumor most frequently localized in thepleura, but it has recently been described in other body sites. We have encountered arare patient with an SFT of the buccal mucosa. We examined the case clinically, histopathologically and immunohistochemically. Dimension of the resected tumor was 3 by
2.5 by 3 cm. Histological observation revealed that the tumor was composed of spindleor ovoid-shaped cells with varying amounts of haphazardly arranged collagen bundles.
Immunohistochemically, the tumor cells exhibited strong staining with CD34 and bcl-2
but were negative to smooth muscle actin, ckit and S-100 protein. The patient was discharged 7 days after surgery, with no signs of recurrences after 14 months. We reported
a rare case of buccal SFT and reviewed 38 cases of intraoral SFT.
Key words: buccal mucosa; CD34; immunohistochemistry; oral cavity; solitary fibrous tumor

Solitary fibrous tumor (SFT) is a rare neoplasm
composed of spindle cells which Klemperer andRabin (1931) first described in the pleura. In earlyreports, SFT was thought to arise from the mesothelial cell and was once termed localized fibrousmesothelioma (England et al., 1989). However,recent immunohistochemical, ultrastructural andtissue cultural studies have suggested that the origin of this tumor is the mesenchymal tissue (Dervanet al., 1986; Ali et al., 1997). Thereafter, SFTs atalmost every anatomic location have been reported(Goodlad et al., 1991), but very rarely in the oralcavity. In the present paper, we present a case of
SFT originating from the buccal mucosa.

Patient Report
In 2002, a 54-year-old man noticed a mass in theleft buccal mucosa. The mass had been asymptomatic and had not increased in size. In 2003, hevisited a hospital for cytological examination of themass, where its cytology was interpreted as benign.
In March 2004, he was referred to our clinic forfurther examination of the mass.
Intraoral examination revealed a hard, elastic and nontender mobile mass which was about 3
cm in size, 0overlayed by apparent normal buccal
mucosa in its color and texture (Fig. 1). There wasneither swelling of the cervical lymph-nodes nor
any significant change in laboratory data. Magnetic
resonance imaging (MRI) revealed that the lesion
was a well-circumscribed, solid mass measuring

Abbreviations: MRI, magnetic resonance imaging; SFT,solitary fibrous tumor; SMA, smooth muscle actin;
GIST, gastrointestinal stromal tumor

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Fig. 1. An elastic hard mobile mass about 3 cm in size
could be palpated intraorally.

about 3 cm in the right posterior buccal space. Themass showed a signal intensity homogeneous withthat of the muscle on both T1- and T2-weighted
images (Fig. 2). Surgical extirpation was performed
under general anesthesia in April 2004. The tumor
surface was smooth and clearly defined and waseasily dissected from the surrounding tissue. Thetumor was oval-shaped, and measured 3 by 2.5 by
3 cm. The cut surface of the tumor was solid, firm,
grayish-white and homogeneous (Fig. 3).
Histologically, the tumor was well-circumscribed and encapsulated with thin fibrous tissues.
The lesion was composed of spindle- or ovoidshaped cells with a various amount of collagenbundles haphazardly arranged. The tumor showeda partially slight storiform pattern appearance (Fig.
4) and was vascularized, occasionally containedareas of dilated vessels with a stag-horn appearance sometimes seen in hemangiopericytoma (Fig.
5). The mitotic count was 0/10 high-power-field.
There was no necrosis.
Through immunohistochemical studies onparaffin-embedded tissue sections, the tumor cells
were strongly positive to CD34 and bcl-2, but
negative to smooth muscle actin (SMA), c-kit andS-100 protein (Fig. 6). These findings resulted in adiagnosis of SFT.
After surgery, the patient improved progressively and was discharged with no difficulty. Since

Fig. 2. MRI shows a well-circumscribed mass about
3 cm in diameter. The mass shows a signal intensity
homogeneous to that of the muscle on both T1- and T2weighted images.

Fig. 3. The cut surface of the tumor is solid, firm, grayish-white and homogeneous.

then, the patient was followed-up for 1 year in theoutpatient clinicand has showed no signs of recurrence as of this writing.

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SFT of the buccal mucosa

Fig. 4. The tumor shows a partially storiform pattern
appearance (hematoxylin and eosin stain). Bar =100 µm.

Fig. 5. The SFT tumor is vascularized and partiallycontains areas of dilated vessels with a stag-horn appearance also occasionally seen in hemangiopericytoma(hematoxylin and eosin stain). Bar = 160 µm.

Discussion
Current advances in immunohistochemical, ultrastructural and tissue cultural techniques havegreatly contributed to studies on SFTs. Since
Gunhan (1994) first described SFT in the oral cavity, many intraoral SFTs were found and 38 patientswere reported in the literature, all of it in English(Gunhan et al., 1994; Suster et al., 1995; Piatteli etal., 1998; Iwai et al., 1999; Kurihara et al., 1999;
Perez-Ordonez et al., 1999; Brunnemann et al.,
1999; Lukinmaa et al., 2000; Alawi et al., 2001;
Hirano et ai., 2001; Kuo et al., 2001; Shin et al.,
2001; Harada et al., 2002; Hardisson et al., 2002;
Vargas et al., 2002; Shnayder et al., 2003; Yanamoto et al., 2003). The clinicopathological featuresof these oral SFT patients including the present
one are summarized in Table 1 with no significant
sex predilection (21 females, 18 males). SFTs

develop in adulthood over a wide age range, andmost are identified between 40s and 70s (mean 51.3years) with tumor sizes varing 8 to 45 mm (mean21.5 mm). Patients with pleural large SFTs havesymptoms such as chronic cough, short of breath,osteoarthropathy, chest pain and hypoglycemia(Weiss et al., 2001). In the present series of studies(Table 1), no such symptoms have been identifiedin patients with intraoral SFT except one. This exception was a female patient with malignant SFT ofthe tongue, and actually had a history of dysarthria
and dysphagia (Shnayder et al., 2003). She was
the only case of malignant SFT of the oral cavity, with a 25-year history of an apparently stabletongue mass. However, the mass increased in size,and her symptoms were aggravated for 6 months
before admission. Therefore, we should suspect77