Classification and Cellular Substrate
Waldenström macroglobulinemia, also known as lymphoplasmacytic lymphoma, is a malignant neoplasm of hematopoietic and lymphoid tissues. It accounts for approximately 5% of all plasma cell disorders. Epidemiologically, the pathology has a distinct profile: the overwhelming majority of affected individuals are males over the age of 50.
The morphological basis of the tumor is the proliferation of B cells. An important feature of the cellular composition is the heterogeneity in the maturity of the elements. The tumor infiltrate contains both small lymphocytes and fully differentiated plasma cells simultaneously. This morphological picture distinguishes the disease from other variants of monoclonal gammopathies.
Immunophenotype and Pathogenesis of Symptoms
The key link in pathogenesis is the secretory activity of tumor cells. They produce a specific paraprotein — the M-component. In Waldenström macroglobulinemia, this component is associated with the monoclonal production of immunoglobulin class M (IgM). Only in very rare cases can the tumor secrete IgA or IgG.
Serum IgM concentration reaches critical levels, ranging between 25–80 g/L. Because the macroglobulin molecule has a large mass and size, its excess in the bloodstream inevitably leads to the development of hyperviscosity syndrome. It is this physicochemical alteration that determines the severity of the patient's condition and the formation of a specific clinical picture associated with impaired blood rheology.
Clinical Presentation and Differential Diagnosis
The clinical manifestations of Waldenström macroglobulinemia comprise two main syndromes: tumor infiltration and hyperviscosity.
Tumor B cells infiltrate lymph nodes, bone marrow, and the spleen. In terms of organ involvement, the disease closely resembles other lymphomas. However, there is a crucial differential diagnostic criterion: unlike multiple myeloma or bone forms of solitary plasmacytomas, Waldenström macroglobulinemia does not exhibit bone resorption (osteolysis).
Hyperviscosity syndrome manifests with the following symptoms:
- Neurological abnormalities: due to central nervous system hypoxia, patients complain of marked dizziness, visual impairment, and paresis.
- Hemorrhagic diathesis: small hemorrhages occur in the mucous membranes. The pathogenesis of these bleedings is twofold: they are caused both by mechanical disruption of blood flow in the microvasculature and by secondary platelet dysfunction.
Prognosis and Association with Other Pathologies
The prognosis for lymphoplasmacytic lymphoma remains guarded. Patient survival averages no more than 5 years.
For a deeper understanding of the pathology, it is important to distinguish it from other B-cell malignancies. For example, heavy chain diseases secrete only immunoglobulin H-chains (gamma, mu, delta, or alpha), which also carries a poor prognosis. In primary immunocyte-associated amyloidosis, tumor B cells produce light chains that partially degrade and deposit in tissues as AL amyloid.
Unlike these conditions, Waldenström macroglobulinemia is characterized by the production of full-length yet excessive IgM without mandatory amyloidosis formation or isolated heavy-chain secretion. It is also worth noting solitary plasmacytomas, which account for 3–5% of monoclonal gammopathies. When presenting with extramedullary localization (e.g., in the lungs or upper respiratory tract), the disease is curable surgically combined with chemo- and radiotherapy, whereas lymphoplasmacytic lymphoma is systemic in nature.