WHO (World Health Organization) grading of CNS tumors is based on histological characteristics such as cellularity, mitotic activity, pleomorphism, necrosis, and endothelial proliferation (neoangiogenesis). It is used in the WHO classification of CNS tumors.
It should be noted that at the time of writing (June 2016), increased importance has been given to molecular markers, both in terms of determining a specific diagnosis and in prognosis. For example, an IDH wildtype low grade diffuse astrocytoma is known to have a poor prognosis compared to IDH mutated tumors.
WHO grade I: lesions with low proliferative potential, a frequently discrete nature, and the possibility of cure following surgical resection alone.
WHO grade II: lesions show atypical cells that are generally infiltrating in nature despite low mitotic activity and they recur more frequently than grade I malignant tumors after local therapy. Some tumor types tend to progress to higher grades of malignancy.
WHO grade III: lesions with histologic evidence of malignancy, including nuclear atypia/anaplasia and increased mitotic activity; these lesions have anaplastic histology and infiltrative capacity; they are usually treated with aggressive adjuvant radiotherapy and/or chemotherapy.
WHO grade IV: lesions that are mitotically active, necrosis-prone, and generally associated with neovascularity and infiltration of surrounding tissue, a propensity for craniospinal dissemination, and a rapid postoperative progression and fatal outcomes; the lesions are usually treated with aggressive adjuvant therapy, typically Stupp protocol combined chemoradiotherapy.
Related Radiopaedia articles
- WHO classification of CNS tumors
- WHO grading of CNS tumors
- VASARI MRI feature set
- diffuse astrocytoma grading
- grade I:
- grade II:
- grade III
- grade IV:
- glioblastoma vs cerebral metastasis
- radiation-induced gliomas
- gliomatosis cerebri (growth pattern)
- specific locations
- treatment response
- Stupp protocol
- glioma treatment response assessment in clinical trials
- multicentric glioblastoma
- multifocal glioblastoma
- prognostic genetic markers