Gliomas are, as a rule, locally invasive. The vast majority of relapses are local; remote metastases resulting from spreading via the blood stream or the cerebrospinal fluid rarely occur. As a rule, however, the gliomas involve larger parts of the brain than is seen from the MR images.
Medullablastomas/PNET/germinomas/plexus choroideus carcinomas
Medullablastomas, PNET, germinomas and plexus choroideus carcinomas spread via the cerebrospinal fluid to the subarachnoid space craniospinally. This has consequences for the primary treatment. Remote metastases outside the craniospinal space as a consequence of hematogenic spreading are very rare.
Meningiomas grow along the brain membrane and can thus invade and obstruct the large venous sinus, and encircle the brain arteries and cranial nerves. Local invasion in overlying bone is not unusual and is not considered a sign of malignancy on its own. Direct invasion into the brain occurs very rarely.
The challenges and limitations of surgical removal of meningiomas are mainly determined by the degree of invasion in the venous sinuses and the degree of encircling of the arteries and cranial nerves.
Remote metastases resulting from spreading via the blood stream or cerebrospinal fluid occurs very rarely.
Metastases to the brain from extracranial tumors
Hematogenic spreading from the primary tumor in other organs can result in metastases to the brain.
The primary tumors are usually localized in the:
- skin (melanoma)
- digestive tract
- urinary tract
The risk of developing brain metastases varies a great deal between the various types of tumor. Patients with malignant melanoma and testicular cancer have a 50 % risk of developing brain metastases, while patients with cancer of the lung, kidney or breast have a 10-20 % risk. Patients with prostate cancer and cancer of the stomach, on the contrary, have very little risk of developing brain metastases.