Breaking boundaries: A rare case of glioblastoma with uncommon extraneural metastases: A case report and literature review.

Introduction: Extraneural metastases (ENM) from glioblastoma (GBM) remain extremely rare with only a scarce number of cases described in the literature. The lack of cases leads to no consensus on the optimal treatment and follow-up of these patients. Research question: Do patient or tumor characteristics describe risk factors for ENM in GBM patients, and is it possible to identify mechanisms of action? Material and methods: This study presents a 55-year-old man with diagnosed GBM who was referred to a CT due to reduced general condition and mild back pain which revealed extensive systemic metastases. A literature review was conducted to identify potential patient or tumor characteristics that may serve as risk factors for metastasis. Results: ENM from GBM are likely underreported, with limited examples in the literature and low survival rates of only a few months. Certain clinical and histopathological factors, such as male sex, younger age, temporal lobe location, and specific biological markers, have been associated with a higher likelihood of metastasis formation. Bone and/or bone marrow metastases are the most common sites. Despite various treatment regimens being attempted, there is no consensus on the optimal therapeutic approach for this patient group. Conclusion: Clinical and histopathological factors can aid clinicians in recognizing the potential for ENM in GBM patients. Our review identifies some of the possible patient- and tumor-related risk factors. However, further research is crucial to identify specific molecular markers and elucidate the underlying biological mechanisms that is essential for development of targeted therapies.