Hello from JustAnswer.
In this context, it is referring to follow-ups to the colorectal procedures that you underwent, and since biopsies were taken, a discussion of the results of the biopsies.
There is no standard medical abbreviation of fups that refers to a diagnosis. In addition, it would be very unusual for a letter to contain the name of a diagnosis without an explanation of the diagnosis. Even communicating a diagnosis by letter would be unusual, but to do so without any explanation would be even more unusual.
If I can provide any additional information, please let me know.
Please let me know if I can provide any further assistance.