Intracranial Solitary Fibrous Tumor: A "New" Challenge for PET Radiopharmaceuticals

Abstract

Solitary fibrous tumor (SFT) of the central nervous system, previously named and classified with the term hemangiopericytoma (HPC), is rare and accounts for less than 1% of all intracranial tumors. Despite its benign nature, it has a malignant behavior due to the high rate of recurrence and distant metastasis, occurring in up to 50% of cases. Surgical resection of the tumor is the treatment of choice. Radiotherapy represents the gold standard in the case of post-surgery residual disease, relapse, and distant metastases. In this context, imaging plays a crucial role in identifying the personalized therapeutic decision for each patient. Although the referring imaging approach in SFT is morphologic, an emerging role of positron emission tomography (PET) has been reported in the literature. However, there is still a debate on which radiotracers have the best accuracy for studying these uncommon tumors because of the histological or biological heterogeneity of SFT.

Keywords: PET/CT; fluorocholine; fluorodeoxyglucose; hemangiopericytoma; non-FDG radiopharmaceuticals; solitary fibrous tumor.

Figure 1

A 69-year-old male patient with a second loco-regional recurrence of left supraorbital solitary fibrous tumor. (A) A brain MRI scan revealed on axial MRI T2c+ a rounded lesion on the lateral side of the left orbit, strongly suspected of disease relapse (red arrow). (B) Two weeks later, ¹⁸F-FDG PET/CT showed no radiopharmaceutical uptake in the left supraorbital region (red arrow). (C) Conversely, after seven days, ¹⁸F-FCH PET/CT showed intense uptake in the aforementioned lesion (red arrow; SUVmax 6.8).