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CLTann,
The grading system is actually an average of three different dimensions of the tumor: cell divison or proliferation, cell structure, and nuclear grade. Each of these elements gets a score from 1 to 3. Theoretically, you could have a tumor that was scored highly on the two non-proliferation elements, yet was very slowly dividing. In that case, the Ki-67 probably would not correlate well with the grade. The text from the article I posted reflects that, as a general rule, the higher the grade, the more proliferative the tumor, which seems logical. Whether grade alone can be seen as a surrogate for proliferation is probably pushing the envelope a bit. For example, my own pathology has an aggressive element (Her2 3+ by IHC) but relatively low proliferation (Ki-67 11%), and the pathogist assigned a grade II based on the three elements. The feature that was scored the highest on my report was neither the proliferation nor the nuclear grade, but the cell structure - apparently my tumor cells were highly undifferentiated, meaning that if they were able to take up residence in a "new neigborhood," so to speak, they would have little problem blending in. What I take from the entire Ki-67 discussion is that there is no single element that we can point to that will lead to a definitive answer - there are just a million pieces to a jigsaw puzzle, and no one knows how they all come together yet.
Hopeful
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