Lymphomas are a heterogeneous group of tumors arising in the reticuloendothelial and lymphatic systems. The major types are Hodgkin lymphoma and non-Hodgkin lymphoma (see table Comparison of Hodgkin Lymphoma and Non-Hodgkin Lymphoma Comparison of Hodgkin Lymphoma and Non-Hodgkin Lymphoma ).
Lymphomas were once thought to be absolutely distinct from leukemias Overview of Leukemia Leukemia is a malignant condition involving the excess production of immature or abnormal leukocytes, which eventually suppresses the production of normal blood cells and results in symptoms... read more . However, better understanding of cell markers and tools used to evaluate those markers now show that the distinction between these 2 cancers is often vague. The notion that lymphoma is relatively restricted to the lymphatic system and leukemias to the bone marrow, at least in early stages, is also not always true.
Malignant lymphoma cells can populate the bone marrow and the blood as well as the lymph nodes. This is more common in the low grade, or indolent, non-Hodgkin lymphomas Non-Hodgkin Lymphomas Non-Hodgkin lymphomas are a heterogeneous group of disorders involving malignant monoclonal proliferation of lymphoid cells in lymphoreticular sites, including lymph nodes, bone marrow, the... read more , such as chronic lymphocytic leukemia Chronic Lymphocytic Leukemia (CLL) Chronic lymphocytic leukemia (CLL) is characterized by progressive accumulation of phenotypically mature malignant B lymphocytes. Primary sites of disease include peripheral blood, bone marrow... read more /small lymphocytic lymphoma (CLL/SLL) or marginal zone lymphoma and the more aggressive mantle cell lymphoma.