[Transformation of malignant non-Hodgkin's lymphomas from low- to high-grade malignancy].

Clinical and histological findings of six patients with low grade non-Hodgkin lymphoma (NHL) which transformed to high grade tumours are reported: 5 out of the 6 cases showed transformation from the centroblastic-centrocytic type to the centroblastic-polymorphic type (Kiel classification). Clinical aggressivity, large tumour mass, high frequency of extranodal sites of disease, systemic symptoms and resistance to treatment were observed. This type of transformation is not rare, estimated to be about 20 p. 100 of cases in the literature, and is more common than Richter's syndrome in chronic lymphocytic leukaemia.