Types of brain tumors

Classification approaches to the separation of detectable brain tumors are determined mainly by two tasks. The first of them is the designation and evaluation of an individual variant of the anatomical and topographical features of the location of the brain tumor with respect to the choice of an operative intervention option or the definition of an individual tactic of conservative treatment, predicting its outcomes. Based on this, the following variants of classification of brain tumors have been developed.

With respect to the outline of the cerebellum, supratentorial and subtentorial tumors are isolated, as well as tumors of the so-called double localization: supra-subtentorial.

To denote the latitude of the spread of the tumor process relative to the cranial cavity, intracranial, extracranial, intra-extracranial, and craniospinal tumors are isolated.

To denote the relation of the tumor node to the cranial vault of the brain tumor, it is customary to divide into a convective and basal (basis - base).

The anatomical relation of the tumor node and the brain makes it possible to isolate intracerebral and extramarginal tumors, which are most often attached to the cranial nerves, brain envelopes, surrounding tissues.

To display the number of detectable tumor foci, the concept is used (singularities and multiplicities are metastatic tumors, cerebral tumors in neurofibromatosis, etc.).

The anatomical relationship of the diagnosed tumor site to the focus of the primary onset of the tumor (which, however, may necessarily be outside the cranial cavity) allows the isolation of primary and secondary (metastatic) brain tumors.

The second approach to Classification is determined by the need to display pathohistological and, therefore, biological properties of the tumor, which in clinical terms is of decisive importance when choosing a method of treatment, assessing its possible volume and radicality, and also in predicting the course of the disease. In general, the modern version of the histological classification of brain tumors has the following form.

I. Tumors of the brain of neuroectodermal tissue.

• Glial tumors:
  • astrocytic tumors (astrocytoma, astroblastoma, anaplastic astrocytoma);
  • oligodendrocyte tumors (oligodendroglioma, anaplastic oligodendroglioma);
  • undifferentiated glial malignant tumors (glioblastoma, brain gliomatosis).
• Tumors of ependyma (ependymoma, subependymoma, malignant ependymoma) and neuroepithelial component of vascular plexuses (papilloma, malignant papilloma).
• Tumors of the pineal gland (pinealoma, pinealoblastoma).
• Neuronal tumors (neurocytoma, neuroblasgoma),
• Undifferentiated malignant neoplasms of neuro-ectodermal type (medulloblastoma, medulloepithelioma, primitive spongioblastoma).
• Tumors of the membranes of the cranial nerves;
  • glial type (neurinoma (schwannoma), malignant schwannoma);
  • mesenchymal type (neurofibroma, malignant neurofibroma - neurogenic sarcoma).

II. Tumors of the brain, consisting of cells of mesenchymal origin.

• Tumors of the membranes of the brain (meningioma, arachnoid-endothelioma), meningosarcoma, xanthomatous tumors);
• Vascular tumors (hemangioma, hemangiosarcoma, angio-reticulum),
• Primary malignant lymphomas.
• Tumors that grow from surrounding tissues (chondroma, chordoma, sarcoma, osteoma, osteoblastoma, olfactory neuroblasgoma, etc.).

III. Tumors before the pituitary: pituitary adenomas (acidophilic, basophilic, chromophobic, mixed), adenocarcinoma of the pituitary gland.

IV. Dizontogenetic brain tumors and tumor-like processes originating from embryonic tissue cells: craniopharyngioma, dermoid cyst, colloid cyst III of the ventricle, heterogeneous cyst, neuronal gammarthroma of the hypothalamus.

V. Dizontogenetic brain tumors originating from highly embryonic cells: teratomas, germinoma, embryonic cancer, choroid carcinoma).

VI. Metastatic brain tumors: lung cancer (50%), breast cancer (15%), hypernephroma (5-10%), melanoma of the skin (10.5%), malignant tumors of the gastrointestinal tract (9.5%) and urinary tract (2%),

This classification is based on the ratio of tumor cells to the derivatives of a particular embryonic leaf, which is determined primarily on the basis of pathological examination using general and special methods of coloring and studying at the level of the raccoon microscope. Recently, the identification of the cell type is based on clearer criteria: by examining the expression of marker cells for each cell of the normal organism of genes (immunohistochemical study).

In some cases, the above classification (or its variations) is referred to as histogenetic. But this does not mean that brain tumors, designated according to the type of cells defined in their structure, are derived from mature cells of the same species. The attribution of the detected tumor, for example, to neurocytomas reflects only the fact that the cells, its constituents, have an origin and a morphology similar to neurons of the brain. But this does not mean that the cells of the tumor originated from mature neurons of the brain.

In addition, there are other points in the histological classification that require further clarification, which will be determined by the development of knowledge about the ontogenesis of the brain and the biology of stem cells. For example, hormone-producing tumors of adenohypophysis, as well as craniopharyngiomas, can be defined as ectodermal tumors, since it is from this germ sheet that the Rathke pocket is formed that gives rise to the adenohypophysis.

So, among primary brain tumors, tumors of neuroectodermal, mesenchymal, ectodermal type, as well as tumors derived from stem cells with a high level of potency (plurinotent stem cells) can be isolated.

According to the time of clinical manifestation of the neoplasm of the brain it is customary to divide into congenital (symptomatology first manifested during 60 days after birth) and acquired.

As in general oncology, the determination of the degree of malignancy is applicable to brain tumors, but the quantitative characteristic of this quality is based solely on the histological, immunohistochemical criteria described for tumors of other localizations. There is no rigid link between the concept of malignancy and the clinical picture that reflects its degree in tumors of other localizations. The growth of any tumor within the cranial cavity, regardless of the degree of its malignancy according to histological criteria, sooner or later (determined by the location of the tumor node or the rate of tumor growth) leads to a fatal outcome, which is clinically one of the main manifestations of malignancy.

In addition, intracerebral neuroectodermal tumors are most often not surrounded by a capsule and are characterized by an infiltrative diffuse type of growth, which is characteristic of malignant tumors. And only for such brain tumors as, for example, meningiomas, neurinomas, ependymomas, the more expansive type of growth is more characteristic.

Metastatic brain tumors are more often located on the border between the gray and white matter of the brain, in the tissues of the cranial nerves, along the vessels of the brain and sinuses of the dura mater, which is determined by metastasizing the tumor cells from the primary focus. Multiple metastases are most often observed in pulmonary tumors and melanoma, while single metastasis is seen with mammary tumors, hypernemia.

Tumor cells enter the brain in a hematogenous way, through the arterial bed, less often - using the venous vessels of the spine. In a predominant mass, brain tumors do not produce metastatic growth, but in those rare cases when metastasis occurs, it is carried out through the system of liquorocirculation (medulloblastoma) and, apparently, by tissue taxis and the homing of tumor stem cells (glioblastoma).