advanced iq Benign tumours are low grade which is slow growing, contained, less likely to spread, and unlikely to return after removal. On the other hand, malignant or cancerous tumours are high grade which means they are fast growing, spread to surrounding tissues, and are more likely to return after removal. Cancerous tumours are further divided into primary and secondary tumours. Primary cancerous tumours originate within the brain itself while secondary tumours are a result of metastasis from tumours in other organ systems, commonly from the lungs. Primary tumours are rarer and the most common types of primary brain tumours are gliomas and meningiomas.