Advanced Deep Learning Architectures in MRI-Based Brain Tumor Classification: A Systematic Review Focused on...

Deep learning (DL) is increasingly applied to automate brain tumor classification from magnetic resonance imaging (MRI), yet meaningful clinical deployment remains limited by tumor heterogeneity, dataset bias, and incomplete tumor-specific validation. This systematic review synthesizes developments from 2016 to 2025 in advanced DL-based MRI brain tumor classification, with a specific emphasis on meningioma-focused classification and subtyping, given their persistent underrepresentation in AI research. Fifty-six eligible studies were analyzed and organized into five methodological categories: transformer-based models; transformer-based feature extraction pipelines; attention-enhanced convolutional neural networks (CNNs); federated learning approaches; and emerging or unconventional DL strategies. Among studies reporting class-wise metrics (n = 19), attention-enhanced CNNs and hybrid CNN-transformer architectures showed high overall accuracy with fewer extreme drops in meningioma performance (F1-score, 89.0% to 99.0%) than end-to-end transformers (F1-score, 79.0% to 97.0%), despite the latter achieving high peak accuracies. Our analysis also showed a marked gap between general tumor categorization and clinically actionable subtyping or grade classification, particularly for meningiomas, reflecting both limited meningioma-targeted tasks and reduced transparency in per-class reporting. Study design and reporting practices limited cross-study comparability, with heavy reliance on a small number of publicly available datasets, frequent class imbalance disadvantaging meningioma representation, and approximately 60% of studies not specifying MRI sequence details. Although predictive performance improved and some studies incorporated interpretability or clinical decision-support components, reporting remained sparse, reinforcing the translational gap between methodological progress and deployment readiness. Finally, publication activity accelerated sharply after 2023 but remained geographically concentrated, raising concerns about representativeness. Our findings call for standardized per-class reporting, greater diverse datasets, interpretability components, and clinically aligned meningioma evaluations to support effective translation into practice.