Solitary fibrous tumors (SFT) are derived from mesenchymal cells originating mainly from the pleura, and cases arising in the head and neck region are rare (especially those that bleed). Many studies reporting tongue SFT treatments exist (1-6), but none have focused on the usefulness of preoperative arterial embolization. According to a recent systemic review of the literature that analyzed 2,629 studies on oral and maxillofacial SFT (7), larger tumors are more likely to be malignant and more aggressive, necessitating a complete excision. For bleeding oral tumors, it is necessary to consider the surgical procedure carefully because bleeding during surgery and postoperative care may lead to incomplete resection and airway problems. We treated a 32-year old woman with a gradually increasing and dysarthria of hypervascular tongue SFT by applying preoperative arterial embolization and then removed the tumor safely and completely. At the time of this report, two years have passed without recurrence.

A 32-year-old woman without remarkable medical or family histories had been aware of a mass on the lower surface of her tongue that had increased in size for half a year before her first consultation. Her face was bilaterally symmetric without regional lymph node swelling, but we noticed she had dysarthria (probably due to the mass). Her routine laboratory blood work was normal. We found an elastic and hard 30-mm tumor in the right lower part of the tongue. Non-contrast-enhanced computed tomography (CT) images revealed a tumor shadow with a clear border and uniform margins in the right sublingual gap. Dynamic CT images of arterial phase showed a strong enhancement with the inflow from an enlarged right lingual artery thought to be a nutrient vessel. Dynamic CT images of venous phase showed washed out contrast media. Non-contrast-enhanced T1-weighted images showed many point-like low and high signal areas, which is called a salt and pepper appearance. T2-weighted image consisted mainly of high signals compared with spinal cord and was partly accompanied by a cord-like low signal area. An ultrasound showed a pulsatile blood flow signal into the mass. We did not perform a histopathological examination to avoid massive bleeding. We diagnosed the patient with hypervascular tongue tumor, and at this stage, paraganglioma was suspected.

We performed a transarterial embolization for the right lingual artery embolization with 300-500 and 500-700-µm embosphere microspheres (BioSphere Medical) through a vascular catheter the day before the operation. The angiography after the embolization confirmed the disappearance of the dense tumor (Fig. 1). The next day, we completely excised the encapsulated tumor under general anesthesia with little to no bleeding during the operation. The size of the resected specimen after surgery was 31x28x18 mm, which was slightly smaller than the size from preoperative CT findings. In addition, the tumor was wrapped in a thin fibrous capsule with a reddish white and solid appearance.

Pathology reported disordered growth of the tumor cells with different densities, and an intricate structure and floral arrangement. In addition, the tumor presented a cleft-like blood vessel, and a staghorn-like blood vessel cavity.

Immunohistochemical staining showed spindle cells with CD34-positive diffusivity, and scattered positive STAT6 spindle cells. S-100 protein was negative. The final diagnosis based on findings was tongue SFT (Fig. 2).

SFT was first reported as a pleural tumor in 1931 by Klemperer and Rabin, and since a long time it has been thought to be derived from the pleura (8). According to the 2013 WHO bone/soft tissue tumor classification, the tumor is a moderate malignant tumor and rarely occurs in the oral region (9). Few polycystic SFTs on the tongue have been reported.

Histopathological findings of SFTs show horn-like blood vessels and tumor cells distributed in a ‘pattern-less’ pattern. According to Chan's diagnostic criteria, CD34 is an effective diagnostic marker (10). Robinson et al (11) described 51 SFTs with NAB2 and STAT6 genes fusions. Thus, we evaluated both markers (CD34 and STAT6) in our patient. Since this case was that of a hypervascular tumor, histopathological examination was not performed before surgery. In the image, paragangliomas indicate the differential diagnosis.

The first choice of treatment is surgical resection, and preoperative embolization is effective for highly irrigated tumors to avoid intraoperative bleeding and incomplete removal, which leads to high local recurrence rates (12). SFT surgery combined with preoperative vascular embolism has already been reported (13-16), but not in the tongue. Intraoperative and postoperative bleeding can also lead to airway problems. To avoid unnecessary tracheostomy and ligation of the maxillary artery, preoperative vascular embolism may be considered aggressively when removing large tumors or tumors with high blood flow. In the case of our patient, we embolized the right lingual artery on the day before the resection, and were able to excise the encapsulated tumor successfully under general anesthesia the next day with little to no bleeding.

Many SFTs are benign and have a relatively good prognosis. However, this tongue tumor is considered to be of intermediate malignancy, and Fletcher et al (9) have reported a 10% recurrence rate. In some cases, recurrences or metastases have been reported after more than 10 years, and follow-ups are required for at least the first two years after the resection (17). In addition to regular contrast-enhanced CT examinations, we will consider abdominal ultrasonography and chest radiographs. At the time of this report, 2 years have passed and the patient has followed a good course without recurrence. We plan for a long-term follow-up.

We treated a patient with tongue SFT by applying preoperative arterial embolization, and then removed the tumor safely and completely. Transarterial embolization should be actively combined with surgery for safe and reliable removal of hypervascular oral tumors in the oral cavity.