Pathology of lymphoma progression

Reflecting the stepwise process of oncogenesis, lymphomas may cumulatively develop a more aggressive phenotype during the course of disease, a process referred to as lymphoma progression, Although morphological, clinical and biological aspects of lymphoma progression do not always overlap, changes i n lymphoma morphology frequently indicate alterations in the clinical and b iological behaviour of the disease. Indolent and aggressive lymphomas in di sease progression can either be clonally related or represent clonally unre lated neoplasms. We propose to use the term 'lymphoma progression' in a bio logical sense denoting only clonal development of and within a lymphoma ent ity. The term 'composite lymphoma' should be used as a merely descriptive m orphological designation for different lymphoma entities in one individual irrespective of clonal relationship. Many types of aggressive B-cell non-Ho dgkin's lymphomas and Hodgkin's lymphomas are reported to secondarily devel op in lymphoma progression. Genetic changes associated with lymphoma progre ssion frequently abrogate the differentiating effects of alterations occurr ing in indolent lymphomas, leading to increased cell proliferation. Within different lymphoma entities, high-risk disease variants mimicking lymphoma progression exist.