9765/1 MGUS


Tumours of haematopoietic and lymphoid tissues
ICD-O-3 topography code: C42 and C77

/span>GUS is defined as the presence in the serum of an M-protein <30 g/L, bone marrow (BM) clonal plasma cells <10%, no end organ damage (CRAB: hypercalcemia, renal insufficiency, anaemia, bone lesions) and no evidence of B-cell lymphoma or other disease known to produce an M-protein (Table 10.04). Although it reflects the presence of an expanded clone of immunoglobulin-secreting cells, this process is not considered neoplastic since it does not always progress to overt malignancy. The presence of a small IgM paraprotein (IgM MGUS) is associated with a clone of lymphoplasmacytic cells that may progress to a lymphoplasmacytic lymphomaand/ or Waldenstr?m macroglobulinemia(WM). Non-IgM MGUS (IgG, IgA) is associated with the presence of clonal plasma cells, and may progress to a malignant plasma cell neoplasm. Although the two forms of MGUS may be identical in their clinical presentation, they have a different genetic basis and different outcomes in terms of malignant progression.