Grading of the tumors of the central nervous system
The concept of grading of the tumors of the central nervous system, agreeing for such the regulation of the "progressiveness" of these neoplasias, dates back to 1926 and was introduced by P. Bailey and H. Cushing, in the elaboration of what turned out the first systematic classification of gliomas.
In the following, the grading systems present in the current literature are introduced. Then, through a table, the more relevant are compared.
/9 malignant neoplasia, uncertain if primitive or secondary
For the concepts of benign and malignant neoplasia see Tumor and Cancer. For primary and secondary neoplasias see Metastasis. A brain tumorcomposed of benign cells, but located in a vital area, can be considered to be life-threatening — although the tumor and its cells would not be classified as malignant.
Kernohan grading
The Kernohan grading system defines progressive malignancy of astrocytomas as follows:
Grade 1 tumors are benign astrocytomas.
Grade 2 tumors are low-grade astrocytomas.
Grade 3 tumors are anaplastic astrocytomas.
Grade 4 tumors are glioblastomas.
St Anne-Mayo grading
The St Anne-Mayo grading system also is used to grade astrocytomas; however, this system uses four morphologic criteria to assign a grade: a) nuclearatypia,
The St. Anne-Mayo grade has four categories of tumors:
Grade 1 tumors do not meet any of the criteria.
Grade 2 tumors meet one criterion, usually nuclear atypia.
Grade 3 tumors meet two criteria, usually nuclear atypia and mitosis.
Grade 4 tumors meet three or four of the criteria.
WHO grading
The World Health Organization grading system is contained in the volumeHistological Typing of Tumours of the Central Nervous System, whose first edition dates back to 1979, the second to 1993 and last one to 2007. The WHO grade has four categories of tumors:
Grade I tumors are slow-growing, nonmalignant, and associated with long-term survival.
Grade II tumors are relatively slow-growing but sometimes recur as higher grade tumors. They can be nonmalignant or malignant.
Grade III tumors are malignant and often recur as higher grade tumors.
Grade IV tumors reproduce rapidly and are very aggressive malignant tumors.
From the histological point of view the WHO system is based on the same criteria as the St Anne-Mayo system.
Comparison of the grading systems
In the following table the various grading systems are compared :
