Editing Brain tumor (section)

=====By behavior=====
Brain tumors can be [[cancerous]] (malignant) or non-cancerous (benign). However, the definitions of malignant or benign neoplasms differ from those commonly used in other types of cancerous or non-cancerous neoplasms in the body.
In cancers elsewhere in the body, three malignant properties differentiate benign tumors from malignant forms of cancer: benign tumors are self-limited and do not invade or metastasize. Characteristics of malignant tumors include:<ref>{{cite journal | vauthors = Louis DN, Perry A, Wesseling P, Brat DJ, Cree IA, Figarella-Branger D, Hawkins C, Ng HK, Pfister SM, Reifenberger G, Soffietti R, von Deimling A, Ellison DW | title = The 2021 WHO Classification of Tumors of the Central Nervous System: a summary | journal = Neuro-Oncology | volume = 23 | issue = 8 | pages = 1231–1251 | date = August 2021 | pmid = 34185076 | pmc = 8328013 | doi = 10.1093/neuonc/noab106 }}</ref>
* uncontrolled mitosis (growth by division beyond the normal limits)
* [[anaplasia]]: the cells in the neoplasm have an obviously different form (in size and shape). Anaplastic cells display marked [[pleomorphism (cytology)|pleomorphism]]. The [[cell nuclei]] are characteristically extremely hyperchromatic (darkly stained) and enlarged; the nucleus might have the same size as the [[cytoplasm]] of the cell (nuclear-cytoplasmic ratio may approach 1:1, instead of the normal 1:4 or 1:6 ratio). [[Giant cells]] – considerably larger than their neighbors – may form and possess either one enormous nucleus or several nuclei ([[syncytium|syncytia]]). Anaplastic nuclei are variable and bizarre in size and shape.
* invasion or infiltration:
** Invasion or invasiveness is the spatial expansion of the tumor through uncontrolled mitosis, in the sense that the neoplasm invades the space occupied by adjacent tissue, thereby pushing the other tissue aside and eventually compressing the tissue. Often these tumors are associated with clearly outlined tumors in imaging.
** Infiltration is the behavior of the tumor either to grow (microscopic) tentacles that push into the surrounding tissue (often making the outline of the tumor undefined or diffuse) or to have tumor cells "seeded" into the tissue beyond the circumference of the tumorous mass.
* [[metastasis]] (spread to other locations in the body via lymph or blood).