The level of differentiation was the first piece of evidence I researched on the way to becoming my own advocate. The second was the term "focally invasive". Theses are all subcomponents of your staging. See:

http://www.oralcancerfoundation.org/facts/stages_cancer.htm

Differention is also covered here as well and refers to the grading of your tumor.

These terms are critical to understand the exact magnitude of your cancer and what tools should be used to fight it. Since the medical diagnosis is typically of few words, every word has a specific meaning and must be studied one at a time, particularly if you are going to be your own advocate. I remember asking Brian to help me define "focally invasive" back in 2003.

The following site below explains differentiation quite clearly, complete with comparative pathology images:

http://books.google.com/books?id=-sfJeOq731MC&pg=PR30&lpg=PR30&dq=poorly+differentiated+SCC-+definition&source=web&ots=0EScaNO8qm&sig=6pBTbvBTScHMtWw2jETayMRRHOM&hl=en&sa=X&oi=book_result&resnum=3&ct=result#PPR30,M1

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