The doctors tell you what it is. A tumour. An Astrocytoma. It is difficult to distinguish between tumour and healthy brain tissue. I never understood that bit. A tumour is one of those round things, right. You can see it clearly on a scan. Or at least under a microscope, it should be clear that you are looking at tumour cells. But apparently in JD’s case, this was not possible. The biopsy was inconclusive and the Astrocytoma diagnosis is based on ‘best guess’.