So, my understanding is that f3 is
bridging fibrosis with areas of scarring that are connected by scar tissue, and f4 is
bridging fibrosis with increased areas of scarring that are connected by scar tissue and nodules. With f4 there is also an increased overall area of scarring throughout the liver. As OH said, a biopsy is only a small section, and it is up to the pathologist to determine if the slice is representative of the overall health of the liver.