Neuroepithelial tumors, including diffuse gliomas and embryonal neoplasms, remain among the most lethal cancers despite major advances in molecular diagnostics and some novel targeted therapies for subsets of patients. A persistent barrier to progress is the lack of a unifying framework that integrates their cellular hierarchy, spatial heterogeneity, and distinctive patterns of progression. In this review, we synthesize converging evidence that neuroepithelial tumor biology represents a pathologic re-enactment of brain ontogeny. Integrating molecular, single-cell, histoarchitectonic, and anatomic observations, we propose that neoplastic transformation, aberrant lineage commitment, and dedifferentiation mirror and invert physiological ontogenetic trajectories. This ontogenetic logic provides a coherent explanation for key hallmarks of neuroepithelial tumors, including intratumoral mosaicism, directional anatomic spread, and the emergence of therapy-resistant tumor-propagating cell states. Ontogenetic multimodal integrated therapy is an anatomy-guided strategy that aligns neurosurgery, radiotherapy, and pharmacotherapy with tumor stage and ontogenetic architecture. By shifting emphasis from radiologically visible tumor bulk to compartment-based developmental logic, this framework offers testable hypotheses and a clinically oriented paradigm for diagnosis, treatment planning, and longitudinal monitoring in patients with neuroepithelial tumors.