Anaplastic astrocytoma is an infiltrative tumor, heterogeneous structure, contains cysts, hemorrhages, has perifocal edema and is located predominantly supratentorial, often affecting the cortical areas.
Anaplastic astrocytoma has a heterogeneous structure. The brain regions altered by the tumor have ↑ ↓ MR signal on T1 and T2 due to cysts surrounded in different degrees of perifocal edema.
Anaplastic astrocytomas possess an intrinsic tendency to progress to glioblastoma. The mean age at biopsy is approximately 41 years. This tumor primarily affects the cerebral hemispheres.
There are no clear boundaries between the tumor, edema and unchanged substance of the brain, where, as with microscopy, malignant cells can be detected. Hemorrhagic foci are rare, but convincingly suggest anaplasia.
In neuroimaging, grade III tumors appear much more aggressive than grade II tumors. Heterogeneous signal patterns and a pathologic contrast enhancement are characteristic for anaplastic tumors. On T2 imaging the hyperintense tumor signal cannot be differentiated from vasogenic changes, therefore all of the T2 signal changes are defined as tumor tissue. Intratumoral heterogeneity may also be caused by a prominent hypervascularity of the tumors. Large cystic areas, if present, are an indication of a further malignization of the tumor toward glioblastoma multiforme. Calcifications are best seen on CT while intratumoral hemorrhage is better seen on MRI.
Contrast enhancement can be focal or nodular. Ring-like enhancement is suspicious for a further malignization.
Mass effect, manifested in the dislocation of brain structures, compression of the ventricular system and smoothing of the furrows in the areas adjacent to the tumor.
There are no specific features in anatomical localization, however, the supratentorial structures (frontal and temporal lobe) are more often affected, subtentially much less.
The author of the article: radiologist, Ph.D. Vlasov Evgeniy Alexandrovich
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