68Ga-DOTATATE Uptake in an Endolymphatic Sac Tumor: Radiologic-Pathologic Correlation

Area of Science:

• Oncology
• Nuclear Medicine
• Otolaryngology

Background:

• Temporal bone masses present diagnostic challenges, often requiring advanced imaging.
• Differentiating endolymphatic sac tumors (ELST) from glomus jugulotympanicum (GJT) paragangliomas is crucial for appropriate management.
• Somatostatin receptor imaging is increasingly used in neuroendocrine tumor evaluation.

Purpose of the Study:

• To evaluate the utility of Gallium-68 DOTATATE Positron Emission Tomography/Computed Tomography (Ga-DOTATATE PET/CT) in a patient with a temporal bone mass.
• To assess the diagnostic performance of Ga-DOTATATE PET/CT in distinguishing between an endolymphatic sac tumor and a glomus jugulotympanicum paraganglioma.
• To investigate the somatostatin receptor expression in the diagnosed temporal bone mass.

Main Methods:

• Dedicated CT and MRI were performed for initial evaluation.
• Ga-DOTATATE PET/CT was utilized for functional imaging of the temporal bone mass.
• Surgical resection followed by histopathological examination and immunohistochemical staining for somatostatin receptor type 2A (SSTR2A).

Main Results:

• Ga-DOTATATE PET/CT demonstrated mild radiotracer uptake in the temporal bone mass (SUVmax, 10.9).
• Post-surgical pathology confirmed the mass as an endolymphatic sac tumor.
• Immunohistochemistry revealed SSTR2A expression in the vasculature of the mass but notably absent in the tumor cells.

Conclusions:

• Ga-DOTATATE PET/CT may show variable or mild uptake in endolymphatic sac tumors.
• The absence of SSTR2A expression in tumor cells, despite vascular expression, suggests a potential limitation for somatostatin receptor-based therapies in ELST.
• Histopathology remains the gold standard for definitive diagnosis of temporal bone masses.