Lowgrade Astrocytomas

The low-grade astrocytomas of childhood can be further sub-divided into pilocytic astrocy-tomas, which account for approximately 75% of the group of low-grade astrocytomas, and other histologies, including fibrillary, protoplasmic and gemistocytic tumors, make up the remaining 25%. Pilocytic astrocytomas are histologi-cally composed of fusiform astrocytes, loosely interwoven in a fine fibrillary background. These tumors frequently have a microcystic component, Rosenthal fibers and large macro-cysts. While the most common location of pilo-cytic astrocytomas is in the cerebellum (Fig. 28.2), they can be found in other locations within the CNS, notably the visual pathway and optic chiasm, the brain stem and the cerebral cortex. The biologic behavior of these pilocytic tumors can be quite indolent and, in fact, spontaneous cessation of growth, as well as regression without treatment, has been observed. More commonly, however, these tumors progress slowly and present with symptoms

Fig. 28.2. (Left) Axial gadolinium-enhanced MRI (T1), showing a vermian juvenile pilocytic astrocytoma. Typical of pilocytic astrocytomas, the majority of the mass effect is due to the large cyst, while the enhancing solid portion contributes much less. (Right) Post-operative axial MRI (T1) after gross total resection of the solid portion of the astrocytoma. As the cyst wall is not composed of tumor cells, it is unnecessary, and potentially morbid, to resect the cyst wall.

Fig. 28.2. (Left) Axial gadolinium-enhanced MRI (T1), showing a vermian juvenile pilocytic astrocytoma. Typical of pilocytic astrocytomas, the majority of the mass effect is due to the large cyst, while the enhancing solid portion contributes much less. (Right) Post-operative axial MRI (T1) after gross total resection of the solid portion of the astrocytoma. As the cyst wall is not composed of tumor cells, it is unnecessary, and potentially morbid, to resect the cyst wall.

Cure Your Yeast Infection For Good

Cure Your Yeast Infection For Good

The term vaginitis is one that is applied to any inflammation or infection of the vagina, and there are many different conditions that are categorized together under this ‘broad’ heading, including bacterial vaginosis, trichomoniasis and non-infectious vaginitis.

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