E4567. Gaallium<sup>68</sup>-DOTATATE and F18 FDG PET Imaging of Recurrent and Metastatic Meningioma
  1. Mat Smith; Mayo Clinic Arizona
  2. Kliment Donev; Mayo Clinic Arizona
  3. Harrison Lang; Mayo Clinic Arizona
  4. Bernard Bendok; Mayo Clinic Arizona
  5. Ming Yang; Mayo Clinic Arizona
Chordoid meningiomas, rare variants of meningiomas, are characterized by unique histopathological features and clinical behavior similar to that of other chondroid/myxoid neoplasms of the CNS. Because of its rarity, imaging characteristics of chordoid meningiomas, specifically appearance on <sup>68</sup>Ga DOTATAE PET/CT, have not been well recorded in the literature. We present a case of pathology-proven chordoid meningioma initially imaged with <sup>68</sup>Ga DOTATATE PET/CT, a postoperative course complicated by multiple episodes of local recurrence, and ultimately the extraordinary finding of extradural metastasis on FDG PET/CT. This exhibit underscores the potential for aggressive behavior in chordoid meningiomas while highlighting the imaging characteristics of this rare disease, the importance of close monitoring, and the comprehensive management strategies attempted in managing such cases.

Educational Goals / Teaching Points
Our educational goal is to show that while brain MRI remains gold-standard in diagnosis of meningioma, F18-FDG PET might be useful in distinguishing benign (WHO grade 1) from aggressive meningioma (WHO grade 2 and 3); and evaluating extracranial meningioma metastases in select patients.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
A 69-year-old man being followed with serial MRIs for a previously resected grade 2 meningioma was found to have local recurrence about one year after gross total resection. Staging <sup>68</sup>Ga DOTATATE MIP and fusion CT images showed homogeneous radiotracer uptake in a mass centered in the falx just cranial to the torcula. MRI at that time demonstrated a homogeneously enhancing mass along the medial aspect of the original surgical bed, centered along the falx. Biopsy at that time was consistent with chordoid meningioma. MIP from the PET/CT showed five discrete masses along the cervicothoracic spine. Fusion images from the PET/CT and accompanying CT images show a large extramedullary mass at the C& level along the 2 o’clock margin of the central canal with associated osseous erosions. At the C3 level, there was frank extradural disease with an enhancing soft tissue mass laying along the right lateral aspect of the spinous process on MRI with homogenous FDG uptake on PET/CT fusion images.

<sup>68</sup>Ga-DOTATATE PET is valuable in imaging recurrent and residual intracranial meningioma and may have great theranostic potential in unresectable meningioma. F18-FDG PET plays an important role in imaging aggressive meningiomas and identifying extracranial metastases for estimation of tumor burden.