Diffuse astrocytoma - infiltrative tumor without clear boundaries in reality, with a relative sharpness of the boundary of a macroscopic picture, the prevalence of its cells is wider, slowly but steadily progressing to anaplastic form, affecting any parts of the central nervous system, less often the brain stem and occipital lobes.
This type of tumor typically affects young adults and has a tendency for malignant progression to anaplastic tumors and, ultimately, glioblastoma. Diffuse astrocytomas represent 35% of all astrocytic brain tumors. They may be located in any region of the CNS but most commonly develop in the cerebrum.
The diffuse astrocytoma is characterized by a relatively homogeneous zone ↑ of the MP signal by T2 and Flair, ↓ of the MR signal by T1. On CT, it is manifested by a homogeneous or almost homogeneous structure of density ↓, and can also be → a brain substance. On MRI, grade II astrocytomas present as diffuse infiltrating T2-hyperintense mass lesions without low signal on T1 and missing contrast enhancement in the majority of cases. In the literature, about 20% of grade II tumors have been described as enhancing. The tumors show a slow growth rate and in some cases, secondary lesions without a tumor bridge.
However, in up to 30% of what appear to be low-grade gliomas are in fact grade III or grade IV tumors presenting no or only faint enhancement patterns. Spectroscopic analysis of the MRIs can help to clarify diagnosis but is certainly not definitive.
Macroscopically, the tumor is a clearly delineated area, which does not correspond to the true size of the tumor. The prevalence at the microscopic level goes beyond its apparent boundaries. Diffuse astrocytoma is not characterized by perifocal edema. The mass effect can be minimal.
The author of the article: radiologist, Ph.D. Vlasov Evgeniy Alexandrovich
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