World Health Organization Grade II gliomas and subventricular zone: anatomic, genetic, and clinical considerations.

BACKGROUND

Recent studies suggest a possible origin of human gliomas from subventricular zone (SVZ) stem cells.

OBJECTIVE

To evaluate the relationship of World Health Organization grade II gliomas (GIIGs) with the SVZ and to investigate the presence of different genetic patterns, depending on their relationship with the SVZ.

METHODS

Forty-three consecutive patients were operated on for GIIG. Preoperative fluid-attenuated inversion recovery-weighted magnetic resonance images were reviewed to assess the presence of cortical involvement and the relationship between gliomas and the SVZ. Patients were divided into 2 groups: group 1, tumors in contact with the SVZ; and group 2, tumors not in contact with the SVZ. Preoperative and postoperative tumor volumes were calculated. Genetic analysis was performed to study 1p19q allelic loss.

RESULTS

Twenty-four patients were in group 1 and 19 in group 2. All tumors were in contact with the cortex. Preoperative volume was significantly larger in group 1 than in group 2 (P = .003). The proportion of total and subtotal resections was higher in group 2 (P = .01). Insular tumors never showed 1p19q codeletions. Noninsular tumors exhibited a significantly different incidence of complete 1p19q codeletion, with allelic loss more common in group 1 (P = .03).

CONCLUSION

GIIGs showed a constant relationship with the cortex and a larger volume when they came in contact with the ventricles. A distinct genetic pattern was found in noninsular SVZ GIIGs. This parameter can be considered for therapeutic management.