Waldenström's macroglobulinemia primarily affects which type of cell?

Waldenström's macroglobulinemia is a type of blood cancer characterized by an excess production of immunoglobulin M (IgM) antibodies. This condition is closely associated with lymphoplasmacytoid cells, which are a type of B-cell. These cells have features of both lymphocytes and plasma cells, and they play a crucial role in the disease process by producing large amounts of IgM.

In Waldenström's macroglobulinemia, the malignant proliferation of these lymphoplasmacytoid cells leads to the clinical symptoms and complications associated with the disorder, such as hyperviscosity syndrome, autoimmune phenomena, and hematological manifestations. Thus, the correct answer directly reflects the key pathological cell type involved in this hematological condition.