Pineoblastoma is a malignant neoplasm originating in parenchymal cells of the pineal gland (epiphysis). It is accompanied by occlusive hydrocephalus, damage to the cerebral trunk, cerebellum. It is manifested by symptoms of sharply increased intracranial pressure, visual, oculomotor disorders, sleep disorders, cerebellar syndrome. Pineoblastoma is diagnosed using neuroimaging, cerebrospinal fluid examination, histological analysis of neoplasm tissues. Treatment includes 3 stages: neurosurgical surgery to remove tumor tissues, radiation therapy, polychemotherapy.
General information
Pineoblastoma is a low-grade embryonic tumor, part of the group of neuroectodermal neoplasms. The structure of neoplasia is similar to other malignancies originating in tissues of neuroectodermal origin: retinoblastoma, medulloblastoma. Tumor growth begins in the cells of the epiphysis, a small gland that secretes melatonin, which has a regulating effect on sleep-wake cycles. Pineoblastoma is a rare cerebral tumor that occurs in 0.1% of cases of all intracranial neoplasms. It is observed mainly in childhood. Males suffer more often, but there are no exact figures for the gender distribution of morbidity.
Causes
A malignant tumor of the epiphysis occurs due to mutation of individual pineocytes, which acquire the ability to divide intensively. Mutations are sporadic, which does not exclude the existence of a hereditary predisposition. The exact causes of the cancerous transformation of pineocytes have not been established. Presumably , the following adverse factors have a mutagenic effect:
- Ionizing radiation. It has a damaging effect on the genome of living organisms. Increased radiation background, radiation therapy (treatment of leukemia, cancerous tumors) can provoke the appearance of a cerebral tumor.
- Complicated course of pregnancy. Intrauterine infections, fetal hypoxia, toxic effects (alcohol, drugs, smoking of the expectant mother) lead to a violation of differentiation, a change in the genome of individual cells. After the birth of a child, the progenitor cells preserved in the epiphysis that have not undergone differentiation serve as material for the development of a tumor.
- Carcinogens are substances that can damage the genetic apparatus of cells. Components of food products (preservatives, dyes, flavors), household chemicals, paint and varnish materials can have a carcinogenic effect. Carcinogens entering the body of a pregnant woman affect the child during intrauterine development, when tissues are most vulnerable.
Pathogenesis
The mechanism of occurrence of malignant cells in the pineal gland is unknown. It is assumed that there are multiple changes in the intracellular genetic apparatus, leading to a radical transformation of the cellular properties of pineocytes. The result is uncontrolled reproduction, lack of differentiation of newly formed pineoblast cells. Pineoblastoma is characterized by active infiltrative growth, rapid spread of pathological cells into surrounding tissues. Malignant formation destroys the tissues of the bridge, the medulla oblongata, spreads to the soft meninges, subarachnoid space.
The epiphysis is located near the sylvian aqueduct, through which the outflow of cerebrospinal fluid (CSF) from the third to the fourth ventricle is carried out. The rapidly increasing pineoblastoma squeezes the Sylvian water supply, blocking the cerebrospinal fluid outflow. Cerebrospinal fluid accumulates in the cavity of the III ventricle, occlusive hydrocephalus is formed, clinically manifested by increasing symptoms of intracranial hypertension.
Macroscopically, the pineoblastoma is a tightly elastic formation of brown color. Microscopically, the tumor consists of small monomorphic cells with hyperchromic nuclei. It is characterized by the presence of a large number of tumor-sprouting vessels with endothelial proliferation. Zones of colliquation necrosis and intracellular hemorrhages are determined.
Symptoms
During the manifestation of the disease, the symptoms of intracranial hypertension come to the fore: intense headache, nausea, vomiting, deterioration of visual function. A number of patients have an increase in body temperature. Young children are restless, capricious. Convulsive syndrome may occur. The growth of the tumor in the upper parts of the midbrain leads to strabismus, double vision, bilateral ptosis. Damage to the cerebellum is manifested by cerebellar ataxia: unsteadiness of gait, disproportion of movements, coordination disorder. A change in melatonin secretion causes sleep disorders – patients complain of difficulty falling asleep or note hypersomnia. Possible occurrence of hemiparesis, decreased sensitivity of half of the body, behavior disorder.
Complications
Pineoblastoma is characterized by a rapid increase in intracranial pressure due to occlusion of the cerebrospinal fluid pathways. The situation is aggravated by the germination of neoplasia into the cavity of the III ventricle. Over time, tumor masses fill the lateral ventricles, almost completely obstruct the ventricular system. A significant increase in the volume of the ventricles in a limited intracranial space leads to compression of the brain.
The tendency of pineoblastoma to metastasis causes the formation of secondary metastatic foci in various areas of the brain and spinal cord. A serious complication is hemorrhage into the tumor tissue with a breakthrough of blood into the ventricles. As the pineoblastoma grows, it squeezes and sprouts the tissues of the medulla oblongata, where the vital centers of respiratory and cardiovascular regulation are located. The defeat of the latter causes a fatal outcome.
Diagnostics
Diagnostic search is carried out by specialists in the field of neurology and neurosurgery. Collecting anamnesis gives an idea of the course of pregnancy, childbirth, the postpartum period, time and symptoms of the onset of the disease. Examining the neurological status, the neurologist determines the approximate localization of the pathological process. Further examinations of the patient include:
- Clinical tests. In a general blood test, leukocytosis, signs of anemia are possible. Blood test reveals an increase in ALT, AST, and a decrease in protein concentration.
- Examination by an optometrist. The main technique is ophthalmoscopy. The detection of edema of the optic disc indicates a significant increase in intracranial pressure.
- Examination of cerebrospinal fluid. Allows you to exclude an infectious lesion of the central nervous system. It detects significant cytosis, increased protein concentration, and the presence of tumor cells (pineoblasts). With hemorrhage in the cerebrospinal fluid, red blood cells are determined.
- Neuroimaging. Preference is given to MRI of the brain, at an older age, if there are contraindications to MRI, cerebral CT may be performed. Neuroimaging techniques make it possible to diagnose neoplasia, determine the nature of its growth, establish the localization and prevalence of the process.
- Stereotactic tumor biopsy. It is carried out in complex diagnostic cases to resolve the issue of the expediency of neurosurgical treatment. In most cases, the verification of the neoplasm is carried out by histological examination of the material obtained intraoperatively.
Pineoblastoma is differentiated from benign pineocytoma, other intracranial volumetric formations (tumors, cerebral cyst, abscess), encephalitis, traumatic injuries. With the manifestation of symptoms in the first year of life, it is necessary to exclude congenital anomalies of brain development. In young children, the symptoms of debut (nausea, vomiting, fever) may be mistaken for manifestations of intestinal infection.
Treatment
Previously, conservative management of patients was considered preferable. The use of microsurgical techniques allowed neurosurgeons to increase the radicality of tumor removal, expand the indications for surgery. The modern treatment regimen includes the entire arsenal of oncologists, divided into 3 main stages:
- Surgical treatment. Pineoblastoma is subject to the most radical excision. Contraindications to surgery are the germination of a neoplasm into the brain stem with the threat of intraoperative damage to vital centers, involvement of vascular plexuses in the oncoprocess with the probability of massive bleeding during the operation. Shunting operations are used as palliative techniques and to improve the patient’s condition before radical neurosurgical intervention.
- Radiation therapy. Due to the high malignancy possessed by pineoblastoma, total irradiation of the brain and spinal cord, additional irradiation of the tumor bed is performed. The number of sessions, the radiation load are determined by the radiologist individually, taking into account the age of the patient, the volume of the lesion, etc.
- Polychemotherapy. It is performed in combination with radiation therapy after a neurosurgical operation or as a palliative treatment of inoperable cases. It is prescribed by a chemotherapist, includes a combination of 2-3 cytostatic drugs (vincristine, etoposide, carboplatin). The side effects of chemotherapy require additional symptomatic treatment.
Prognosis and prevention
Pineoblastoma always has a serious prognosis. The fatal outcome is caused by compression of the brain, hemorrhage into the ventricles, damage to the vital centers of the medulla oblongata. Combined three-stage therapy allows to prolong the life of patients. The tendency of the tumor to implantation spread, metastasis causes a high frequency of relapses. The prognosis depends on the age of the patient, the prevalence of the tumor process. In children under 5 years of age, pineoblastoma is characterized by a more malignant course, 5-year survival is observed only in 15% of cases, at the age of 6 years the prognosis is more favorable. In the case of tumor dissemination, patients die within a year from the moment of the debut of clinical symptoms. Since the causes and mechanisms of malignant transformation of pineocytes remain unknown, specific prevention of the disease is not possible.