Telomere erosion and fusion play an important role in the pathology of many common human malignancies, including chronic lymphocytic leukemia (CLL). In this interview, Chris Fegan, MB, MD, FRCP, FRCPath, from Cardiff University, Cardiff, UK, discusses the findings of a study analyzed the telomere profiles of CLL patients, to give a better idea of the replicative history of the disease. The study identified the shortest telomeres ever recorded in primary human tissue, reinforcing the concept that there is significant cell division in CLL. The study also provided evidence that critical telomere shortening, dysfunction and fusion contribute to disease progression. This interview was recorded at the British Society for Hematology (BSH) 2018 Annual Scientific Meeting, Liverpool, UK.