As with any tumour, prostate cancers are described in terms of their grade and stage. The grade relates to the appearance of the cancer cells, as compared with that of the normal parent prostate tissue. The grade varies from low, with appearance similar to prostate cells, to high, with totally rogue cells. It is usual to attempt to quantify the degree of cellular change using a so-called Gleason classification. This measures a level of cellular differentiation between 1 and 10, with a worsening of grade in the higher numbers.