Giant Cell-Rich Solitary Fibrous Tumor in the Nasopharynx: Case Report and Literature Review

Solitary fibrous tumors (SFTs) can occur in several locations outside the pleura, but rarely in the sinonasal tract, and particularly not in the nasopharynx. Herein, we describe an unusual case of giant cell-rich SFT (GCRSFT) occurring in the nasopharynx. A 64-year-old man experienced dizziness and headache for more than 10 years with no obvious cause. Computed tomography (CT) scan showed a 3.9 cm × 2 cm tumor on the posterior lateral wall of the left nasopharynx, and angiography revealed a hypervascular tumor fed by branches of the left carotid artery. Hence, preoperative embolization was performed, and then the tumor was endoscopically resected. The symptoms were relieved after the resection, and postoperative head CT and video laryngoscopy showed that the tumor was completely resected. We next characterized the specific pathological characteristics of the resected tumor. Histologically, the tumor was characterized by varying cellular proliferation of cytologically bland spindle cells within a collagenous stroma, with prominent interspersed branching vessels. Mitotic activity was low (2/50HPF), and there was no evidence of pleomorphism or tumor necrosis. Moreover, multinucleated giant cells with deep nuclear staining and distributed in pseudovascular spaces were found within the tumor. We ruled out the possibility that our case was giant cell fibroblastoma (GCF) by immunohistochemical analysis, showing that the tumor cells were positive for CD34, CD99, STAT6, and BCL-2, and that the Ki-67 labeling index was 3%, indicating that our case was SFT and not GCF. The patient's condition is generally good after a 14-month follow-up. This report serves to broaden the morphologic spectrum of GCRSFT and will help clinicians and pathologists better understand this entity to prevent misdiagnosis.

Keywords: differential diagnosis; giant cell-rich solitary fibrous tumor; nasopharynx.