Okay, I'm going to tentatively offer a possible explanation. I say tentatively, because one of the irritating byproducts of my AN is that I disremember things sometimes. So it's entirely likely that I'm just making this up, but here goes:
This thread triggered a "memory" of a conversation I had with my CK nurse at Stanford when we were viewing my MRIs - pre-op, 6-mo, and 12-mo. In this flashback, she's pointing to the darkened necrosis at 6 months, and the LESS-dark area at 12 months (taken at the same MRI center) and she's explaining that as the tumor changes its cellular structure, it begins to appear white again on the film. She goes on to say that if one waited too long to have a followup MRI, it might be difficult to know whether the tumor had undergone necrosis at all.
Am I hallucinating? Somebody help me out here.