Somatostatin receptor-2 negative meningioma: pathologic correlation and imaging implications.

Meningiomas are the most common non-malignant primary intracranial tumors, accounting for nearly 40% of all primary brain tumors, usually expressing high levels of somatostatin receptors (SSTR), particularly SSTR2. Because Ga-DOTATATE targets SSTR2, it is increasingly used clinically for meningioma evaluation. While previous apparent lack of SSTR expression in meningiomas has been reported in isolated cases, these prior studies utilized Indium-111 (In) Octreotide, which is of lesser diagnostic accuracy compared to Ga-DOTATATE, as well as Technetium-99m (Tc)-DTPA scintigraphy, which necessitates an intact blood-tumor-permeability barrier. This paper presents a histopathologic proven atypical meningioma, WHO Grade II, with low level avidity on Ga-DOTATATE PET/MRI, subsequently proven to be SSTR2-negative by immunohistochemistry, with a review and discussion of the current literature and imaging implications.