Please tell me how long it takes for to diagnois a brain tumor/cancer?

Varies: Diagnosing a brain tumor can be done very quickly if an MRI scan shows typical appearances of a brain tumor. The technology has advanced significantly so that there are specific patterns and appearances of brain tumors. However, to formally diagnose a brain tumor, most require a biopsy. This has the advantage of providing molecular details that may help with treatment and prognosis.

Symptoms?: If the tumor is small and not pressing on vital areas of the brain, depending on the tumor type, if benign or cancerous, it can be present for a very long time and undiagnosed. A very aggressive tumor however, or a tumor that affects an important part of the brain will likely be diagnosed fairly quickly.