Note: Some citations in the text of this section are followed by a level of evidence. The PDQ editorial boards use a formal ranking system to help the reader judge the strength of evidence linked to the reported results of a therapeutic strategy. (Refer to the PDQ summary on Levels of Evidence for more information.)
This classification is based on the World Health Organization (WHO) classification of nervous system tumors. The WHO approach incorporates and interrelates morphology, cytogenetics, molecular genetics, and immunologic markers in an attempt to construct a cellular classification that is universally applicable and prognostically valid. Earlier attempts to develop a TNM-based classification were dropped: tumor size (T) is less relevant than tumor histology and location, nodal status (N) does not apply because the brain and spinal cord have no lymphatics, and metastatic spread (M) rarely applies because most patients with central nervous system (CNS) neoplasms do not live long enough to develop metastatic disease.
Note: Some citations in the text of this section are followed by a level of evidence. The PDQ Editorial Boards use a formal ranking system to help the reader judge the strength of evidence linked to the reported results of a therapeutic strategy. (Refer to the PDQ summary on Levels of Evidence for more information.)
There is no consensus as to the optimal treatment of newly diagnosed craniopharyngioma. Little data exist to compare the different modalities in terms of recurrence rate or quality...
The WHO grading of CNS tumors establishes a malignancy scale based on histologic features of the tumor. The histologic grades are as follows:
WHO grade I includes lesions with low proliferative potential, a frequently discrete nature, and the possibility of cure following surgical resection alone.
WHO grade II includes lesions that are generally infiltrating and low in mitotic activity but recur. Some tumor types tend to progress to higher grades of malignancy.
WHO grade III includes lesions with histologic evidence of malignancy, generally in the form of mitotic activity, clearly expressed infiltrative capabilities, and anaplasia.
WHO grade IV includes lesions that are mitotically active, necrosis-prone, and generally associated with a rapid preoperative and postoperative evolution of disease.
The following outline has been adapted from the WHO classification. Tumors of glial origin are grouped under a common heading, and tumors limited to the peripheral nervous system have been excluded. Some rare or exclusively pediatric tumors are listed below for purposes of classification, but they are not discussed in the text that follows.