Extragonadal Germ Cell Tumor

Diagnosis

Extragonadal Germ Cell Tumor

Diagnosis

Extragonadal Germ Cell Tumor

Discussion

The most common lesions of the suprasellar/sellar region are cranipharyngiomas, pituitary adenomas, meningiomas and Rathke's cleft cysts. Among other lesions, metastatic disease, xanthogranulomas, intrasellar gangliocystomas are infrequent.
In children, the most frequent is pilocytic astrocytoma.
Intracranial germ cell tumors (GCT) are extremely rare, less than 2% of intracranial lesions. According to the WHO classification, subtypes are germinoma, endodermal sinus (yolk sac ) tumors, choriocarcinomas, teratomas ( immature, mature, with malignant transformation) and mixed germ cell tumors.
Clinical presentation depends of the local extension and type of lesion: CRF obstruction at the level of the third ventricule, endocrinopathies, diabetes insipidus, vascular invasion of the deep venous structures and visual symptoms ( Parinaud's Syndrome).
Magnetic Resonance Imaging is the modality of choice for sellar/suprasellar tumors evaluation.
As in brain parenchyma lesions, base of the skull, including the pituitary region, tumors are difficult to detect using FDG PET/CT. Lesions with cystic components will be mostly negative on FDG PET/CT. However, prior to pathological confirmation, FDG PET/CT is useful to rule out the possibility of metastatic disease as the cause of the lesion, may help evaluate the degree of malignancy in teratomas and can detect drop metastases in the spinal cord.
High uptake has been reported in pituitary adenomas, craniopharyngiomas and low uptake in chordomas, meningiomas and Rathke's cleft cysts. Due the frequence, most series address the aspect of pituitary adenomas using FDG PET/CT. In those later cases, the use of corticotropin-releasing hormone has been suggested to increase FDG uptake.
In addition to the pineal and suprasellar regions, extragonal GCT have been imaged using FDG PET/CT in the anterior and posterior mediastinum and in the paravertebral region.

Key points

Low uptake

References

The WHO Classification of Tumors of the Nervous System. P Kleihues et al. K Neuropathol Exp Neurology 2002;61:215-225
Intracranial Germ Cell Tumors. RJ Packer et al. The Oncologist 2000;5:312-320
Primary Intracranial Germ Cell Tumors. B Beard et al. ARRO 2019
The sellar and suprasellar region: A “hideaway” of rare lesions. Clinical aspects, imaging findings, surgical outcome and comparative analysis. I Petrakakis et al. Clin Neurol Neurosurgery 2016;149:154-165
18F-FDG PET and MR Imaging Associations Across a Spectrum of Pediatric Brain Tumors: A Report from the Pediatric Brain Tumor Consortium. K Zukotynski et al . J Nucl Med 2014;55:1473-1480
Analysis of 18F-fluorodeoxyglucose positron emission tomography findings in patients with pituitary lesions. H Seok et al. Korean J Intern Med 2018;28:81-88
PET/MRI in the Diagnosis of Hormone-Producing Pituitary Microadenoma: A Prospective Pilot Study. H Wang et al. J Nucl Med 2018;59:523-528
CRH stimulation improves 18F-FDG-PET detection of pituitary adenomas in Cushing’s disease. J Boyle et al. Endocrine 2019; doi.org/10.1007/s12020-019-01944-7
18F-FDG PET/CT Imaging for Mixed Germ Cell Tumor in the Pineal Region. SA Park et al, Clin Nucl Med 2012;37:e61-e63
Expansive Masses Arising From The Clivus: The Role Of FDG-PET/CT In The Metabolic Assessment Of Skeletal Lesions. A Cistaro et al. J Radiol Case Rep 2009;3:33-40
Preoperative Evaluation of Sellar and Parasellar Macrolesions by [18F] Fluorodeoxyglucose Positron Emission Tomography. M Tosaka et al. World Neurosurg 2017;103:591-599
18F-FDG PET/CT Finding of Drop Metastases from Germ Cell Tumor of Pineal Gland
TK Jain. J Nucl Med Technol 2017;45:114-115
Craniopharyngioma With High FDG Uptake. T Nagata et al. Clin Nucl Med 2012;37:77-79
Primary Paravertebral Germ Cell Tumor Demonstrated by FDG PET/CT. R Wang et al. Clin Nucl Med 2020;45:322-323.