Solitary fibrous tumor of the masticator space – Report of a rare case

The solitary fibrous tumor (SFT) is a potentially malignant spindle cell neoplasm of the mesenchymal origin that was originally described as a thoracic lesion originating from the pleural tissue. Recently, numerous extrapleural sites of origin have been described, also affecting the head and neck region. SFTs are benign in most cases, but 10%–15% of extrapleural SFTs show malignant behavior in the form of recurrent or metastatic disease. We present the case of a 25-year-old female who presented with an asymptomatic left-sided facial swelling of over three years. She had a diffuse swelling in the left preauricular region, extending to the temporal region deep to the zygomatic arch. On magnetic resonance imaging, the vascular lobulated mass occupied the masticator space, infratemporal fossa, and parapharyngeal space, eroding the mandible. An ultrasound-guided fine-needle aspiration cytology was suggestive of SFT, positive for signal transducer and activator of transcription 6 and negative for TLE1. After preoperative embolization, the tumor was excised through a midline lip split approach with posterior segmental mandibulectomy and reconstruction with a titanium plate. Histopathological report was consistent with SFT. Due to high-risk features, she was advised adjuvant radiation therapy. SFTs of the head and neck are exceedingly rare and those with aggressive behavior even more so. To our knowledge, this is the only case of SFT arising in the masticator space. Diagnosis is often difficult and not definitive without immunohistochemistry. In most cases, complete surgical excision is the only treatment necessary. Regardless, all patients require close clinical follow-up for several years.