The pineal gland is an unencapsulated anatomical tissue in the middle of the brain.
Pineal region tumors are very rare and constitute 1% of all brain tumors. In childhood, it is seen at a rate of 8%. Tumors of this region are examined in two groups as germ cell and pineal cell. There are pinealocytes surrounded by astrocytes in the pineal gland structure. While very different tumors are seen due to the different cells in the structure of the pineal gland, approximately 80% of these tumors are malignant in character. The most common malignant pineal tumors are; Germinomas are pineloblastomas and benign pineal tumors are pineocytoma, lipoma, pineal cyst, AVM meningiomas.
Pineal tumor was first described in 1717. In 1913, the first successful pineal tumor surgery was performed.
In recent years, developments in all other departments in medicine, radiological imaging techniques, innovations in neuroanesthesia and intensive care, developments in microsurgery have added new concepts to the pineal tumor approach. In addition, correction of cerebrospinal fluid (CSF) flow in pineal tumors cannot yield acceptable results in pineal region surgeries. Today, side effects and mortality rates in pineal tumor surgeries have been reduced to very low levels. Mortality rates in pineal tumor surgeries are between 0-5%.
Classification of pineal tumors
Pineal tumors are examined in 4 groups
1: Germ cell tumors: It is the most common pineal tumor arising from the gonad tissues. It is more common in males. All germ cell tumors except benign teratomas are malignant. They spread via CSF or systemic route
2: Pineal cell tumors:
a) Pineocytoma: It is a well differentiated tumor originating from pineal cells. It occurs with equal frequency in both sexes. It is known as stage II according to the classification of the health organization (WHO) yesterday and the 5-year survival is known as 85%. It shows a very low rate of malignancy. They are radiosensitive tumors.
b) Pineoblastoma: It is the primitive of the pineal parenchyma and is more common in young adults and men. According to the WHO classification, they are stage 4 tumors. Average survival is 24-30 months.
3:Glial cell tumors. The most common in this group are ependymoma, glioblastoma, anaplastic astrocytoma, oligodendriglioma and choroid plasus papilloma.
4: Mixed cell tumors. meningioma, hemangioblastoma, metastases are examined in this group.
Clinical complaints and findings;
Pineal region tumors cause clinical complaints mainly through 3 mechanisms.
1: Complaints and findings of increased intracranial pressure after inhibition of CSF circulation
2: Direct findings with tumor growth
3: Endocrine complaints
Intracranial Headache, nausea, vomiting, papilledema and diplopia are characteristic due to increased pressure. In addition to the above complaints, upward gaze restriction, nystagmus and papilla abnormality (parinaud’s syndrome) are seen. In addition, cerebellar signs such as ataxia, coordination disorder, tremor may occur due to the pressure of the mass effect of the tumor
Endocrine findings, on the other hand, diabetes insipidus is seen due to the compression of the tumor. In addition, precocious puberty in boys, sexual delay in girls, hypopituitarism, hypernatremia and hyperphagia can be seen due to B-human chorionic gonadotropins released from cells in the content of choriocarcinoma or germinomas.
Diagnosis
The gold standard examination method in pineal region tumors is medicated brain magnetig resonance (MR). MRIs of the spinal canal should be performed in those suspected of spinal cord involvement. Brain tomography with or without contrast is required for differential diagnosis in some pineal tumors, and cerebral vascular angiography is rarely required in those with suspected vascular lesions. Some pineal tumors require tumor markers, which look for B-hCG and Q-fetoprotein from both blood and CSF. For example, increased B_ hCG in CSF mostly accompanies choriocarcinoma, while high Q-fetoprotein is seen in endodermal sinus tumor or embryonal carcinoma or teratomas.
Treatment
It is very important to know the type of tumor properly in the preoperative period in pineal region tumors. In addition, the degree of hydrocephalus caused by the tumor is extremely important. For example, in mild hydrocephalus and if the patient’s CIBA clinic is not advanced, direct surgery may be recommended. However, in advanced hydrocephalus and acute regression due to the clinical hydrocephalus of the patient, emergency surgery is planned following external drainage. In some pineal tumors, stereotaxic biopsy or biopsy with open surgery is recommended in cases where the histopathological diagnosis cannot be made despite CSF cytology and blood tests. Stereotaxic biopsies diagnosis rates in pineal region tumors are over 90%. However, this procedure has 2% mortality and 5-10% morbidity.
Surgical approaches to pineal tumors;
In pineal region surgery, first of all, the diameter of the tumor, its growth pattern, its extension to the adjacent anatomical region and its relations with vascular structures, as well as the degree of hydrocephalus should be known very well. Accordingly, a surgical approach should be planned. First of all, the experience of the surgeon in the approach to these tumors and the surgical corridor he is accustomed to are very important in the rates of death and disability after surgery. In the history of these tumors, shunt operations were performed routinely before the cerebellum surgery for hydrocephalus, but nowadays, with the increase of the surgeon’s experience, this procedure is either not performed at all or a third ventriculostomy is rarely performed. Thus, the post-operative death and disability rates in these patients have been reduced to very low levels. Thanks to micro-surgeons experienced in pineal tumor surgery, very successful surgical results are obtained. If the pineal tumor is prozone pathology germinomas performed during the surgery, radiotherapy should be given as an adjuvant treatment after surgery, since these are radiotherapy-sensitive lesions. If the pathology study performed during surgery is benign lesions, pineocytoma and ependymoma, all of these lesions should be surgically removed. Such lesions do not require additional adjuvant therapy. If the pineal tumor has spread to the spinal cord, the entire spinal canal should be irradiated with radiotherapy. Radiotherapy should not be given in pineal tumors, especially in infants younger than 5 years old. In these cases, the option of chemotherapy should be applied.
In conclusion
The operative mortality in pineal tumor surgery varies between 0-8%. In the pineal tumor surgeries that I have performed since the last 2000, the surgical mortality is 0%. The optimal treatment method in the treatment of pineal tumor depends on the pathological type of the tumor. In benign pineal tumor surgery, 100% cure is achieved with total resection and no additional treatment is required. While 5-year survival is 75% in germinomas, it is around 55% in pineal cell tumors. Today, very successful results are obtained in pineal tumors surgeries in experienced hands.
