User:DerekvG/sandbox/braintumor/astrocytoma

Grading

Of numerous grading systems in use for the classification of tumor of the central nervous system, the World Health Organization (WHO) grading system is commonly used for astrocytoma. Established in 1993 in an effort to eliminate confusion regarding diagnoses, the WHO system established a four-tiered histologic grading guideline for astrocytomas that assigns a grade from 1 to 4, with 1 being the least aggressive and 4 being the most aggressive.

The WHO-grading scheme is based on the appearance of certain characteristics: atypia, mitosis, endothelial proliferation, and necrosis. These features reflect the malignant potential of the tumor in terms of invasion and growth rate. Tumors without any of these features are grade I, and those with one of these features (usually atypia) are grade II. Tumors with 2 criteria and tumors with 3 or 4 criteria are WHO grades III and IV, respectively. Thus, the low-grade group of astrocytomas are grades I and II.

Various types of astrocytomas are given these WHO grades:

Description of Grading	Astrocytomas
:*WHO Grade 1- Consist of slow growing astrocytomas, benign, and associated with longterm survival. They can often be cured by surgically removing the tumor. Even if the surgeon is not able to remove the entire tumor, it may remain inactive or be successfully treated with radiation.	pilocytic astrocytomas, pleomorphic xanthoastrocytomas, subependymal giant cell astrocytomas, and subependymomas are uncommon tumors
:*WHO Grade 2- Consist of are relatively slow-growing, usually considered benign that sometimes eveolve into more malignent or as highergrade tumors. They are prevalent in younger people who are often present with seizures. Median survival varies with the cell type of the tumor. Grade 2 astrocytomas are defined as being invasive gliomas, meaning that the tumor cells penetrate into the surrounding normal brain, making a surgical cure more difficult. People with oligodendrogliomas have better prognoses than those with mixed oligoastrocytomas, who in turn have better prognoses than patients with astrocytomas. Other factors which influence survival include age (younger the better) and performance status (ability to perform tasks of daily living). Due to the infiltrative nature of these tumors, recurrences are relatively common. Depending on the patient, radiation or chemotherapy after surgery is an option.	lowgraded astrocytomas of fibrillary (or diffuse) astrocytomas, oligodendrogliomas, mixed oligoastrocytomas
:*WHO Grade 3- Consist of anaplastic astrocytomas. It is often related to seizures, neurologic deficits, headaches, or changes in mental status. The standard initial treatment is to remove as much of the tumor as possible without worsening neurologic deficits. Radiation therapy has been shown to prolong survival and is a standard component of treatment. In general, median survival ranges from two to three years. There is no proven benefit to adjuvant chemotherapy or supplementing other treatments for this kind of tumor. Although temozolomide is effective for treating recurrent anaplastic astrocytoma, its role as an adjuvant to radiation therapy has not been fully tested.	anaplastic astrocytoma
:*WHO Grade 4-Consists of Glioblastoma multiforme (GBM), which is the most common and most malignant primary brain tumor. Glioblastoma multiforme usually spreads quickly to other parts of the brain. For this reason, these tumors are difficult to treat, and it is common for them to recur after initial treatment. This tumor can occur in all age groups, including children; the average age at which it is diagnosed is 55 years. Symptoms often begin abruptly with seizures. Surgical removal remains the mainstay of treatment, provided that unacceptable neurologic injury can be avoided. The extremely infiltrative nature of this tumor makes complete surgical removal impossible. Although radiotherapy rarely cures glioblastoma, studies show that it doubles the median survival of patients, compared to supportive care alone. The prognosis is worst for these grade 4 gliomas. Few patients survive beyond 3 years. Median survival of GBM victims who forgo treatment is approximately 90 days and is only extended to about twelve months by aggressive surgery, radiation and chemotherapy. Long term survival (at least five years) falls well under 3%.	Glioblastoma multiforme (GBM)

According to the WHO data the lowest grade astrocytomas (grade I) make up only 2% of recorded astrocytomas, grade II 8%, the higher grade anaplastic astrocytomas (grade III) make up 20% of recorded astrocytomas. Finaly the highest graded astrocytoma gradeIV GBM is the most common primary Cancer of the Nervous System and second most frequent brain tumor. Despite the low incidence of astrocytomas compared to other human cancers, mortality is significant, as the higher grades (III & IV) present high mortality rates (mainly due to late detection of the neoplasm).

== Infiltrating low-grade astrocytomas grow slowly compared to their malignant counterparts. Doubling time for low-grade astrocytomas is estimated at 4 times that of anaplastic astrocytomas. Several years often intervene between the initial symptoms and the establishment of a diagnosis of low-grade astrocytoma. One recent series estimated the interval to be approximately 3.5 years. The clinical course is marked by a gradual deterioration in half of cases, a stepwise decline in one third of cases, and a sudden deterioration in 15% of cases. Seizures, often generalized, are the initial presenting symptom in about half of patients with low-grade astrocytoma.

For patients with anaplastic astrocytomas,3 the growth rate and interval between onset of symptoms and diagnosis is intermediate between low-grade astrocytomas and glioblastomas. Although highly variable, a mean interval of approximately 1.5-2 years between onset of symptoms and diagnosis is frequently reported. Compared to low-grade lesions, seizures are less common among patients with anaplastic astrocytomas. Initial presenting symptoms most commonly are headache, depressed mental status, and focal neurological deficits.