How long does it take for a brain tumor to form? is it possible for one to form within 72 day

A : A brain tumor starts when a perfectly well-behaved cell turns into a cell that divides without limit (at least in theory). That change probably occurs in the blink of an eye. So that could be one answer to your question. But, that's probably not the answer you are looking for. You started out with one tumor cell. After a period of time (every day or so), that one tumor cell divides into two. Then, after another day or so, those two cells divide into 4, and so on. After a total of 20 divisions, you would have about 1, 000, 000 tumor cells, enough to make a cube 100 cells on a side (or 1000 micrometers -- or 1 mm). A 1 mm cube can be comfortably seen with the naked eye, if you know where to look. It turns out that a 1 mm cube (called a voxel) is also about the smallest thing that can be seen by most MRI scanners, the device most often used to look for brain tumors. Would a doctor looking at an MRI mention that a 1 mm cube was abnormal? The volume of the brain is about 1, 400, 000 cubic mm, so the answer is "no." an MRI abnormality measuring 1 cm on a side would probably get mentioned, but may not get called a tumor yet. The doctor might call it a "lesion" and suggest another MRI in a few weeks or suggest different tests. 1 cm is 10 mm or 1000 of our cells. A tumor 1000 cells on a side has 1, 000, 000, 000 cells. The tumor would reach this size after a total of 30 divisions. Many brain tumors don't start to cause symptoms until they are about 4 cm on a side (give or take a wide margin). A tumor this size has 64, 000, 000, 000 cells. The tumor would reach this size after a total of 36 divisions. So, it is mathematically possible for a brain tumor to become noticeable within the span of time that you mention.

The : The length of time it takes for an abnormal or cancerous cell to grow into a brain tumor depends on many variables. One of the most important is the grade or aggressiveness of the tumor. Some types of tumors (meningiomas, low-grade astrocytomas, schwannomas, and others) might take years or decades to grow. Other more rapidly dividing and malignant tumors (de novo glioblastoma, metastatic lung cancer, and others) might grow rapidly over the course of a few months. In some cases a slow growing tumor that might have been present for years can "transform" into a more aggressive type and start growing much more rapidly. This is best known in low-grade gliomas that sometimes can turn from "benign" to "malignant".

It is possible: For the most malignant brain tumor, the glioblastoma (gbm) this is possible. It has been reported and I have personally seen patients who have had normal MRI scans done for some non-tumor reason (ie. Head injury). Within three months, they present with neurological symptoms and the large enhancing MRI findings of gbm. The "incubation" time for gbm may be as short as 3 months.