What are the stages of a brain tumor?

There are none: Brain tumors rarely develop extra neural metastases. They are graded based on pathology. Gx cannot be graded, g1 well differentiated, g2 moderately differentiated, g3 poorly differentiated, g4 undifferentiated. The reason why there is rarely metastasis is because the brain does not have a well-developed lymphatic drainage system. Hope this helps.

No staging: Most brain tumors are classified by their degree of resectability. Treatment outcomes are variable depending on the type of tumor (pathology), extent of invasion into surrounding tissues, location of the tumor, and performance and health status. http://www.cancer.gov/cancertopics/wyntk/brain/page1.