Figure 1. Karl Lennert, young pathologist at Erlangen University (picture selected from Professor Karl Lennert’s personal photographic archive digitalised by Stefano A. Pileri upon Professor Lennert’s authorisation).

Figure 2. Professor Lennert’s wife, Doctor Amanda Heyer at the tutorial held in Damp in 1992 (picture selected from Professor Karl Lennert’s personal photographic archive digitalized by Stefano A. Pileri upon Professor Lennert’s authorization).

Professor Karl Lennert passed away in Kiel on 27 August last year. He was born in Fürth on 4 June 1921 and graduated in Medicine from Erlangen University on 27 March 1945. In these early days, he developed his interest in pathology and haematology, being inspired by Alexander Maximow’s studies. In 1945, he entered the Institute of Pathology in Erlangen, where he initiated the career (Figure 1) that led him to Göttingen (Max-Plank Institute), Frankfurt (University Institute of Pathology), Zurich, Heidelberg (University Institute of Pathology, of which he was ad interim Director in 1961) and finally Kiel, where he became Director of the Institute of Pathology of Christian-Albrechts University in 1963. In 1952, he obtained a habilitation in Pathology with a thesis on ‘The histological diagnosis of lymphogranulomatosis’ that inspired the volume ‘Lymph node diagnostics in sections and smears: cytology and lymphadenitis’ in 1961, being Professor of General Pathology and Pathologic Anatomy since 1958. After the publication of this book, that took more than 8 years to write, he said ‘after it was released, my career was done’. In August 1954, Professor Karl Lennert got married to Dr Amanda Heyer (Figure 2). They happily spent almost 58 years together. Amanda, who represented the light in his personal and professional life, passed away in February last year.

In Kiel, Professor Karl Lennert created the Kiel Lymph Node Registry and was Director of the Tumour Centre until 1988, when he retired by remaining as Emeritus Professor and Chief of the Institute of Haematopathology which he had founded in the meantime. He had achieved worldwide recognition, earning five honoris causa Medical Degrees (in Gent, Köln, Xiang, Madrid, and Erlangen-Nürberg, respectively), the Ernst-Jung Prise, the Schleiden, Ashoff, Robert Koch and Rudolf Virchows medals, the Wilhelm-Conrad-Röntgen Prise of the Accademia Nazionale dei Lincei, and the Fred W. Stewart Award (at Sloan Kettering Institute, New York, NY, USA).

Professor Lennert, who was my mentor in Haematopathology, pioneered the present knowledge of malignant lymphomas. By his bright intelligence, spirit of observation, rigorous methodology and strong motivation, he developed a morphological view of the lymphatic tissue that is still the basis of both lymphoma diagnosis and research. Relating lymphomas to possible physiological counterparts of the disease led him to establish a terminology for cells, differentiation and growth patterns which is still an integral part of the current classification. The same theoretical approach has been stimulating molecular lymphoma research over decades using immunoglobulin gene analysis and gene expression profiling to identify and characterise a ‘cell of origin’.

Figure 3. Signing off of the kiel Classification at Amsterdam airport (picture selected from Professor Karl Lennert’s personal photographic archive digitalised by Stefano A. Pileri upon Professor Lennert’s authorization).

Figure 4. Professor Karl Lennert with Professor Jacques Diebold (on the right) at the Tutorial held in Damp in 1992 (picture selected from Professor Karl Lennert’s personal photographic archive digitalised by Stefano A. Pileri upon Professor Lennert’s authorisation).

Figure 5. Professor Karl Lennert with Professor Robert Lukes in 1978 (picture selected from Professor Karl Lennert’s personal photographic archive digitalised by Stefano A. Pileri upon Professor Lennert’s authorisation).

Under his leadership, the Institute of Pathology of the Christian-Albrechts University in Kiel became the reference centre for malignant lymphomas not only in Germany but in Europe, as was the light for several American colleagues. He started the impressive case collection that is still available and represents a true patrimony for the international community, this I had the chance to appreciate during my stay in Kiel in 2009, which represented my last service as President of the European Association for Haematopathology (EAHP).

Professor Lennert was the father of the Kiel Classification that was pivotal to the present classification of tumours of the lymphoid and haematopoietic tissues. In doing this, he looked for an international consensus by first funding the European Lymphoma Study Club and later, the European Lymphoma Study Group, which gave rise to the present EAHP. In this light, the Kiel Classification was cosigned by Remy Gerard-Marchant, Iris Hamlin, Franco Rilke, Alfred G. Stansfeld and Jan A.M. van Unnik (Figure 3). His international spirit led him to establish friendly relationships with many groups and colleagues, including Jacques Diebold and Robert Lukes, pictured left (Figures 4 and 5).

As a scientist and academic, he founded a school, which has generated many leading figures in Germany and all over the world who have continued and expanded his work.

All haematopathologists worldwide will be forever grateful to Professor Karl Lennert for the unique contribution he gave to the onset, development and success of our discipline. The highest medical ethos that was his basic motivation, and marks exactly what historians would call modern pathology, is represented by the first sentence of his habilitation thesis in 1952: ‘There is a widespread opinion that the work of pathologists is limited to post-mortem diagnosis and has no relation to the life as such. It would be sad to the profession of pathologists, if the impulse for work and research would not be based on the care of patients. Only in this way, even a pathologist can be a medicine in the true sense’.

Personally, I will miss Karl Lennert as a mentor and as a friend and will try to honour his memory for the rest of my life. Sit tibi terra levis, Karl!