The metastasis of primary brain tumors is mostly intracranial metastasis

Tumors that grow inside the skull are generally called brain tumors, also known as brain cancer, including primary brain tumors that originate from the brain parenchyma and secondary brain tumors that metastasize from other parts of the body to the skull. So, what are the characteristics of the metastasis of primary brain tumors?

1. There is no obvious correlation between the malignancy of primary brain tumors and metastasis. Its metastasis is mainly intracranial, while extracranial metastasis is less common.

2. Intracranial metastasis is also called implantation metastasis. The conditions for this type of metastasis are that the tumor is rich in tumor cells and less in stroma. Tumor cells are easily shed or tumor tissue is exposed to the cerebrospinal fluid pathway. The shed cells can be carried to a distant place or deposited on the ventricular wall. Tumors that can metastasize intracranial include medulloblastoma in the fourth ventricle and ependymoblastoma on the ventricular wall. In addition, choroid plexus papilloma and other gliomas that protrude into the ventricle can also metastasize intracranially.

3. Surgery may cause intracranial metastasis of the tumor. When the tumor is not close to the ventricles or subarachnoid space, brain surgery, especially tumor biopsy or partial resection, can cause tumor cells to fall off and spread in the subarachnoid space, increasing the chance of brain tumor metastasis.

4. Extracranial metastasis is generally rare. The main reason is that the body's circulatory system has a strong ability to reject free brain tumor cells. In addition, the brain lacks lymphatic channels for metastasis, and most intracranial tumors have high requirements for the growth environment and conditions.

5. Extracranial metastasis is possible. Conditions that hinder extracranial metastasis may disappear as treatment continues, allowing patients to develop extracranial metastasis of the tumor. Contact with the dura mater and extracranial soft tissue during surgery can cause extracranial metastasis. Sometimes tumor cells can directly enter the open lymphatic vessels and vascular cavities, increasing the chances of postoperative tumor recurrence on the dura mater and extracranial tissue. At the same time, tumors can metastasize spontaneously, especially some tumors with greater invasiveness, which can penetrate the dura mater and invade extracranial tissues. Tumors that can metastasize extracranial include gliomas, meningiomas, primary sarcomas, etc.