Endocrine Abstracts

Introduction: Paragangliomas are neuroendocrine tumours, usually found from the base of the skull to pelvis. They are extremely rare in the sellar and parasellar region which normally lacks paraganglion cells. We report a rare case of an incidental sellar paraganglioma.

Case: A 66 years old female had progressive retinopathy and maculopathy of unclear cause since 2011. Lung nodules were seen on CT performed to exclude paraneoplastic retinopathy. 18F-FDG PET/CTscan showed normal lungs but a high uptake (SUV_Max 78.3) in the pituitary. MRI pituitary showed a new lesion (not visible on MRI brain done 5 years before). Serial MRI scans over 10 months showed growth from 8×4×5 mm to 11×8×7 mm with no impingement of the chiasm (or field defect) or cavernous sinus invasion. Pituitary function tests were normal except partial diabetes insipidus on formal water deprivation test. Although she was asymptomatic, increasing size, uncertain diagnosisand PET avidity led to an uncomplicated transsphenoidal pituitary resection. There was appearance of a complete resection on post-surgery MRI scan. Biopsy showed a low-grade parenchyma tumour of the pituitary gland with overall morphology and immunophenotype suggestive of a paraganglioma with low MIB-1 immunoreactivity (<1%). Plasma metanephrines, MRI Neck, Thorax, Abdomen, and Pelvis were normal and analysis of the FH, MAX, RET, SDHA, SDHB, SDHC, SDHD, SDHAF2, TMEM127 and VHL genes did not detect a pathogenic variant.

Discussion: Incidence of focal 18F-FDG uptake in the pituitary gland is reported between 0.07 and 0.8% and follow up investigations with MRI and histology showed that nearly half were non-functioning pituitary adenoma, followed by Langerhans cell histiocytosis, hypophisitis and, metastasis. 18F-FDG avidity of paragangliomas have been reported to show higher SUV avidity for malignant than benign lesions and for extra-adrenal paragangliomas. The avidity of the tumour in our case was high and therefore careful radiological follow up is warranted. Sellar or para-sellar paraganglioma is extremely rare and only numbered cases are reported. Most of the sellar paragangliomas presented as pituitary masses on MRI or CT scan causing local invasion and the size and invasiveness has made them difficult to resect completely. Diagnosis is made based on characteristic histology features (zellballen pattern) and immunopositivity for synaptophysin and S-100 protein as none of the reported cases presented with features of catecholamine excess or radiological features to distinguish it from pituitary macroadenoma. This case was unusual as it presented as a growing microadenoma with high 18F-FDG-PET avidity. Rarer causes of PET avidity should be considered when assessing these lesions.