This composite educational figure illustrates the neuroimaging and histopathological features of a pilocytic astrocytoma (WHO Grade 1). Panel A displays an axial T1-weighted post-gadolinium MRI of the brain, showing a discrete, well-circumscribed, intensely enhancing nodular lesion located in the temporal lobe. Notably, there is an absence of perilesional vasogenic edema or significant mass effect on the adjacent parenchyma. Panel B provides a corresponding high-magnification light microscopy view of the tumor using Hematoxylin and Eosin (H&E) staining. The histology demonstrates a classic biphasic pattern characterized by 'piloid' cells—astrocytes with elongated, hair-like bipolar processes. Diagnostic hallmarks visible include Rosenthal fibers, which appear as brightly eosinophilic, worm-like proteinaceous aggregates, and a background of fibrillary matrix. These visual findings correlate with the slow-growing, benign nature of this pediatric-type diffuse low-grade glioma, frequently associated with MAP kinase pathway alterations.

This medical comparison chart displays axial brain MRI sequences and corresponding histopathological whole slide images (WSI) for three glioma subtypes: Glioblastoma (G), Oligodendroglioma (O), and Astrocytoma (A). The MRI modalities include T1-weighted, T1-gadolinium contrasted (T1-Gd), T2-weighted, and Fluid-Attenuated Inversion Recovery (FLAIR). The Glioblastoma row shows a large, heterogeneous mass with significant peripheral enhancement on T1-Gd and extensive hyperintense peritumoral edema on T2 and FLAIR images. The Oligodendroglioma and Astrocytoma rows demonstrate smaller, less infiltrative masses with varying signal intensities. The final column displays Hematoxylin and Eosin (H&E) stained WSI biopsy sections, illustrating the histological differences in tissue architecture and cellularity between the subtypes, such as the more fragmented appearance of the oligodendroglioma sample compared to the more cohesive astrocytoma section. This visual resource is intended for neuroradiology and pathology education, emphasizing the integration of multi-modal imaging and histology for definitive brain tumor classification.

Imaging modality: light microscopy of a hematoxylin and eosin stained brain tissue section from a cerebral hemisphere tumor. Primary subject: diffuse astrocytoma, WHO Grade II (infiltrating astrocytoma). Specimen: brain parenchyma/tumor tissue. Imaging perspective: microscopic histology field. Anatomical context: central nervous system, brain (cerebral hemispheres), intra-axial glial neoplasm displaying diffuse infiltration. Visual features: moderately increased cellularity with mildly enlarged, variably hyperchromatic nuclei; mild nuclear pleomorphism; delicate, interconnected astrocytic processes creating a fibrillary background; abundant eosinophilic cytoplasm in some astrocyte-like cells; absence of overt necrosis or microvascular proliferation in this field; mitotic activity not evident at this magnification. Pathology: low-grade, infiltrative glioma consistent with WHO Grade II astrocytoma; preserves overall brain architecture; growth pattern extraparenchymal infiltration challenging complete resection; lacks features defining higher grades (no brisk mitoses, microvascular proliferation, or necrosis). Diagnostic significance: confirms low-grade astrocytic neoplasm; implications for prognosis and management; potential progression to higher-grade gliomas (III–IV) with time or treatment resistance; imaging correlation with MRI typically demonstrates non-destructive, infiltrative lesion; informs surgical planning, adjuvant radiotherapy/chemotherapy decisions; differential considerations include oligodendroglioma and pilocytic astrocytoma in specific contexts. Clinical relevance: presents with seizures/ focal deficits in adults (4th–6th decades), guiding neuro-oncologic workup and longitudinal surveillance. This image exemplifies low-grade glial tumor histology.

Magnetic Resonance Imaging (MRI) of the brain, axial plane, with gadolinium contrast, including post‑contrast T1-weighted sequences and accompanying T2/FLAIR imaging. A left occipito‑temporal intra-axial mass is evident, showing irregular, ill‑defined enhancement after contrast with surrounding vasogenic edema and mild mass effect on adjacent cortex and sulci. The radiographic phenotype is most compatible with an infiltrative glial neoplasm of intermediate to high grade, with differential diagnosis including anaplastic astrocytoma versus glioblastoma. Perfusion or spectroscopy data (not shown) would further aid grading and treatment planning. The patient underwent surgical resection. Histology demonstrated astrocytic tumor cells with increased cellularity, nuclear pleomorphism, and brisk mitotic activity, without definitive necrosis, consistent with anaplastic astrocytoma (WHO Grade III). Location in the left occipito‑temporal region correlates with potential language and visual processing effects and explains seizure propensity. Imaging features—irregular enhancement, infiltrative margins, edema, and no definite necrosis—support high‑grade designation, though overlap with Grade IV lesions exists. Clinically, these tumors are managed with maximal safe resection followed by radiotherapy with concomitant and adjuvant temozolomide; MGMT status may influence prognosis. This case exemplifies imaging‑pathology correlation in adult supratentorial gliomas and informs differential diagnosis, surgical planning, and oncologic management discussions for neuroradiology, neuro-oncology, and neurosurgical trainees. Case courtesy of Radiopaedia, Dr. Frank Gaillard.