Pathology-proven extradural ("distant") metastases of gliomas in adults in the Netherlands between 1971 and 2018: a systematic case series.
Background
Diffuse gliomas are the most frequent primary tumors originating in the central nervous system parenchyma. Although the majority of these tumors are highly malignant, extradural metastases (EDM) are extremely rare. We aimed to perform a systematic review of patients with pathology-proven EDM of diffuse gliomas in the Netherlands.


Methods
From the Nationwide Network and Registry of Histo- and Cytopathology in the Netherlands information on all cases with EDM between 1971 and October 2018 was retrieved. Patients aged < 18 years or with a diagnosis of ependymoma or continuous tumor growth from intradural to extradural were excluded. Demographics, initial tumor diagnosis, treatment characteristics, location of the EDM, and survival data were collected. IDH1 R132H immunohistochemistry was performed on cases in which a paraffin block of the metastatic tumor could be retrieved.


Results
Twenty-five patients with diffuse glioma and pathology-proven EDM were identified. Median age at diagnosis of glioma was 46 years (IQR: 35-59); 21 patients (84%) were male. Histopathologic diagnosis was glioblastoma in 17 patients (68%) and lower-grade tumor in eight patients. In 3 out of 12 patients of which a paraffin block could be retrieved immunohistochemistry revealed an IDH1-mutant glioma. Most frequent EDM locations were bone/bone marrow (14/25 patients; 56%), and lymph nodes (6/25 patients; 24%).


Conclusion
EDM of diffuse glioma are rare. They occur most frequently in patients with glioblastoma, however, they can also originate from lower-grade, IDH-mutant gliomas. In daily practice, EDM of diffuse glioma should be considered in patients with tumefactive lesions of the bone or lymph nodes.
['den Hartog|Sanne J|SJ|https://orcid.org/0000-0002-1650-951X', 'van der Kolk|Anja|A|', 'Bruggink|Annette|A|', 'Seute|Tatjana|T|', 'Wesseling|Pieter|P|', 'Wilbers|Joyce|J|']
extradural metastases glioma histopathology