MORPHOLOGYTypically,themarrowcontainsaninfiltrateoflymphocytes,plasmacells,andplasmacytoidlymphocytesinvaryingproportions,oftenaccompaniedbymastcellhyperplasia.Sometumorsalsocontainapopulationoflargerlymphoidcellswithmorevesicularnuclearchromatinandprominentnucleoli.Periodicacid-Schiff-positiveinclusionscontainingimmunoglobulinarefrequentlyseeninthecytoplasm(Russell bodies) orthenucleus(Dutcher bodies) ofsomeoftheplasmacells.Atdiagnosisthetumorhasusuallydisseminatedtothelymphnodes,spleen,andliver.Infiltrationofthenerveroots,meninges,andmorerarelythebraincanalsooccurwithdiseaseprogression.
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Immunophenotype. The lymphoid component expresses B cell markers such as CD20 and surface immunoglobulin, whereas the plasma cell component secretes the same immunoglobulin that is expressed on the surface of the lymphoid cells. In almost all tumors, the secreted immunoglobulin is an IgM.
Clinical Features. The dominant presenting complaints are nonspecific and include weakness, fatigue, and weight loss. Approximately half the patients have lymphadenopathy, hepatomegaly, and splenomegaly. Anemia caused by marrow infiltration is common. About 10% of patients have autoimmune hemolysis caused by cold agglutinins, IgM antibodies that bind to red cells at temperatures of less than 37°C.
Patients with IgM-secreting tumors have additional signs and symptoms stemming from the physicochemical properties of IgM. Because of its large size, at high concentrations IgM greatly increases the viscosity of the blood, giving rise to a hyperviscosity syndrome characterized by the following:
Visual impairment associated with venous congestion, which is reflected by striking tortuosity and distention of retinal veins; retinal hemorrhages and exudates may also contribute to problems with vision
Neurologic problems such as headaches, dizziness, deafness, and stupor, all stemming from sluggish venous blood flow
Bleeding related to the formation of complexes between macroglobulins and clotting factors as well as interference with platelet function
Cryoglobulinemia resulting from the precipitation of macroglobulins at low temperatures, which produces symptoms such as Raynaud phenomenon and cold urticaria
Lymphoplasmacytic lymphoma is an incurable progressive disease. Because most IgM is intravascular, symptoms caused by the high IgM levels (e.g., hyperviscosity and hemolysis) can be alleviated temporarily by plasmapheresis. Tumor growth can be controlled with low doses of chemotherapeutic drugs and immunotherapy with anti-CD20 antibody, and recent work has shown that BTK inhibitors are also effective. Transformation to large-cell lymphoma occurs but is uncommon. Median survival is about 4 years.
Hodgkin lymphoma encompasses a distinctive group of neoplasms that are characterized by the presence of a tumor giant cell, the RS cell. Unlike most NHLs, Hodgkin lymphomas arise in a single lymph node or chain of lymph nodes and typically spread in a stepwise fashion to anatomically contiguous nodes. Although the Hodgkin lymphomas are now understood to be unusual tumors of B cell origin, they are distinguished from the NHLs by their unusual pathologic and clinical features.