Professor Daniel (Danny) Catovsky one of the most influential and internationally renowned hematologists died on December 2, 2022, after a short illness.

He came to prominence as a research fellow in the MRC Leukaemia Unit at the Hammersmith Hospital and Royal Postgraduate Medical School (RPMS) which he joined in 1967. Under the directorship of David Galton, he and John Goldman flourished at a time when immunological and cytogenetic findings were first being applied for the diagnosis, classification, and treatment of leukemias. Daniel with David Galton formed the outstanding British team in the French/American/British (FAB) Group who classified leukemias and myelodysplasia. This classification laid the foundations for the subsequent WHO Classifications of the Hematological Neoplasms. Daniel focused on chronic lymphoid leukemias while John Goldman specialized in chronic myeloid leukemia (CML), both rapidly becoming world authorities in their chosen fields. Daniel pioneered research into the pathogenesis of CLL and into its treatment at a time when interest in this disease, the most frequent leukemia in western countries, was minimal compared to that in acute leukemias and CML. His research in hairy cell leukemia was pivotal to its diagnosis and treatment, and he was also a pioneer in the characterization of B- and T-cell chronic prolymphocytic leukemia, splenic lymphoma with villous lymphocytes and adult T-cell leukemia/lymphoma.

He was promoted to the lecturer, then senior lecturer and in 1987 to a full professorship at the RPMS. In 1988 he moved to the Royal Marsden Hospital as Head of Hematology and Professor of Hematology at the Institute for Cancer Research where he was to serve for the rest of his career, from 2003 as Emeritus Professor and Fellow in the Division of Molecular Pathology at The Institute of Cancer Research, London.

He co-ordinated the first four UK CLL Trials. He had the wisdom to ensure the storage of samples from these trials and this foresight provided him and his colleagues with a wealth of well-documented material to which new molecular techniques could be applied. With his team he made fundamental observations on the pathogenesis of CLL, the prognostic and therapeutic significance of the immunological, cytogenetic and molecular genetic findings and on the familial occurrence of the disease. He published over 760 research papers, chapters and reviews as well as editing or authoring seven books. He became one of the most cited researchers in the fields of hematology and medical oncology.

Nationally he was President of the British Society of Haematology (BSH, 1996–1997) and from1999 Fellow of the Academy of Medical Sciences. In 2000 he was awarded the BSH Medal for his contributions to British hematology. He trained numerous research fellows from all over the world, many of whom are now internationally known, and he supervised 15 MD and PhD theses.

Internationally he served on the editorial boards of a number of scientific journals including the British Journal of Haematology, Leukemia Research, Leukemia and Lymphoma and Clinical Oncology, as well as reviewing countless articles submitted to these and to other leading journals. He was Visiting Professor in New York, Toronto, Nebraska, Indiana, San Diego, Chicago and Houston, and gave the first Ham-Wasserman lecture at ASH in 1984. He was also a Faculty Member of the European School of Hematology (ESH). Daniel chaired or served as a committee member for numerous national and international data monitoring, scientific and grant-awarding boards for clinical trials and basic research. He also chaired the subcommittee responsible for the WHO classification of chronic lymphoid leukemias. In 2005 he received the IWCLL Binet-Rai Medal for his outstanding research into CLL.

Above all Daniel was loved by his many students, research fellows, colleagues and patients for his warm, compassionate character. He was an inspiring teacher and mentor, a wonderful role model for anyone aspiring to a career in academic medicine. He never lost his Spanish accent, acquired in Argentina where he was born on the 19th of September 1937 and where he qualified in medicine in 1961. He had many tragedies in his personal life to overcome. He suffered the loss of a brother who “disappeared” in 1976 during the rule by the country’s military dictatorship. He and his wife Professor Dame Julia Polak then suffered the tragic death in 2011 of their daughter Marina who was killed, when crossing London Bridge, by a negligent motorcyclist. Julia herself died in 2014, 19 years after undergoing heart-lung transplantation for pulmonary hypertension. Despite these tragedies, Daniel managed to retain his tremendous consideration and support for those who needed him and his enthusiasm for clinical and basic research. His impact was enormous on all those who came into contact with him, and who will not forget him as a great doctor, wonderful colleague and the warmest of friends.

Second International Conference on Hairy Cell Leukemia, Leeds Castle, Kent, September 22–24, 1986. The three chairmen, Daniel Catovsky, Harvey Golomb, David Golde are at the center of the front row.