Temporal Glioblastoma Mimicking Basal Ganglia Invasion: Distinguishing Removable and Unremovable Tumors.

Objective: Maximal safe resection prolongs the survival of patients with glioblastoma (GB). However, whether total resection of the enhanced lesion is pursued or abandoned depends on preoperative judgments based on the findings of magnetic resonance imaging (MRI). Anatomically, medial temporal tumor tends to invade toward the temporal stem, insula, and basal ganglia, representing tumor with high surgical risk. In the present study, we describe the key radiologic features of medial temporal GB to achieve extent of resection.

Methods: We reviewed all GB cases located in the temporal lobe (tGB) treated between April 2013 and March 2018 at Kitasato University Hospital. On the basis of MRI, tGB was simply classified into 3 groups: medial tGB and nonmedial tGB, and medial tGB was further subdivided into invading type and mimicking type. We focused on the resectability of medial tGB.

Results: Twenty-seven patients with tGB were identified. Twenty were included in the nonmedial tGB, and 7 were in the medial tGB. All medial tGB seemed to invade into the basal ganglia and/or the lenticulostriate arteries, but detailed examination revealed 2 types of tumor, invading type (3 cases) and mimicking type (4 cases). The invading type had true involvement of the basal ganglia and/or lenticulostriate arteries, whereas the mimicking type had no involvement of these structures. This new classification is highly effective, as the former is unresectable, but the latter is totally resectable.

Conclusions: Medial tGB is a challenging tumor for maximal safe resection, so our classification will help to identify cases of removable medial tGB.