Data is meaningless without context and without knowing how reliable it is.
PSA tests, for example, provide data that sent a lot of people to an early grave, or to years of unnecessary treatment and anxiety.
I think about that a lot when people in various forums (including this one) cite academic papers or other information from areas they aren't experts in. They may be correct (technically correct), and have the correct data, but context might they be missing?
(The 50% number was of samples sent to a lab. Doctors aren't in the habit of taking random healthy people's lymph nodes and sending them for biopsy, so those patients had other symptoms of lymphoma that triggered the need for a biopsy of suspicious lymph nodes.)