Sometimes cancer cells proliferate in different ways and indeed there are different types of Prostate Cancer (PCa). Some are not considered significant and in such cases normal HIFU may not be directed at these but only where a small tumour or small number of tumours is/are considered significant. This means the Prostate can maintain more function. But cancer cells apart from congregating, can develop in a way that they do not form a solid tumour and be dispersed whether within the Prostate or further afield, so finely that they can't be seen on even a good MRI scan. (The consultant illustrated this with his pepperpot example). Where the cancer cells are more concentrated they are easier to direct HIFU to. The consultants also have to take into account additionally, the grade of the cancer, the volume and position. Perhaps, this is partly the reason why HIFU is not recommended for all men and why subsequent changes can require further HIFU or even more radical treatment. Of course surgery can remove all the cancer cells within the Prostate but there is a limit to how far the surgeon can cut and even then there is a small risk that in the process some cancer cells may escape. Sometimes a surgeon can have a good idea of the extent of the cancer whilst removing the seen cancer, by sending samples to a lab in the course of operating and better examination of the Prostate in the lab after removal. Unfortunately, nothing is certain with PCa. Cancer cells that have remained dormant for a very long time can become active again and respond differently to treatment. It can be many years before a man can consider himself cured and so the term 'In remission is used'. We know that most men that have PCa whether diagnosed with it or not go on to die of something else. Sadly, for a minority of men this is a killer disease and they are fighting a retreating battle and as with any forum, this one it is used disproportionately by those most severely affected.