I thought I'd reply as CGIN tends to be less usual and can cause a lot of worry. It often co-exists with CIN3 or CIN2, which is what happened in my case.
I was referred for a colposcopy last summer - where the consultant explained that the abnormality was "glandular" which could mean one of a number of things, most of them not cancer or even pre-cancer and he would have a look - didn't see very much and he took a biopsy and it came back 2 weeks later as CIN3. When I went in to get the LLETZ treatment, the consultant (a different one) said that she would remove about a cm as it seemed likely that the lesion spotted went further up the cervical canal, given the fact that my smear registered a glandular (and not squameous) abnormality. A few weeks ago I was advised by the clinic that the biopsy taken from the LLETZ had returned a diagnosis CGIN and CIN3. The clinic explained that there were no cancerous cells found, but that as these are precancerous and COULD progress to cancer, they like to be sure etc etc. The consultant had checked the file and my case would be referred to an MDT meeting - they discussed the case and decided that the margins were clear, and asked me to come back for a check up (which i did last month). All seems to be fine and there don't seem to be any side effects. According to the clinic, they monitor CGIN more closely because it is less visible and because they know less about how it progresses...
However, in terms of what CGIN means, my understanding is not so much that it is more agressive. In fact, my nurse, doctor etc have all said there is nothing more worrying about it at all. But rather that it is harder for medical staff to actually see what is going on because the cells affected are inside the cervical canal. Because CIN3 etc affects the cells outside, on the face of the cervix, a bit of solution and white marks appear and everything is visible in the microscope. The same is not true with CGIN.
Therefore its not a case of aggressiveness/quicker progression etc but that they have to be sure they have removed it all, which is why they often refer to MDT meetings, and do further treatment. The reason why theysometimes have to go back and do more, according to the nurse I saw, is that they prefer to take a little, and then take some more, rather than remove massive areas of unaffected cervix.
Hope this helps. I imagine they will give you another LLETZ and then confirm clear margins.... it's a bit of a hassle and more waiting and worrying, but it's only so they can be 100 per cent sure that the whole lot is gone with a clear margin around the affected area.