Hematological neoplasms are tumors of cells in different states of maturation and differentiation. Since monoclonal gammopathies (MG) refer to B mature lymphocyte neoplasms, lymphogenesis should be well known. We must keep in mind that the last stage of maturation of these lymphocytes is the plasma cell. This is how a MG could appear in the context of a plasma cell neoplasm, such as multiple myeloma or amyloidosis, but also in relation to a lymphoma. A monoclonal peak is produced by mature B lymphocytes or plasma cells that secrete a monoclonal protein (Immunoglobulin), and represents a MG. But it must be emphasized that, in the correct clinical context, a hypogammaglobulinemia can represent a MG as well. Another important point is the understanding and interpretation of requested tests, such as protein electrophoresis (PEP), immunofixation (IFx) or serum free light chains (sFLC). The current MG screening panel includes these three studies (PEF, IFx, sFLC), although a simpler panel measuring PEF and sFLC has also been proposed, but not yet formally validated. Therefore, screening done only with PEP is insufficient.