Monoclonal gammopathy of undetermined significance  (MGUS)

• M-protein in serum <3 g/dL.
• Bone marrow clonal plasma cells <10% and low level of plasma cell infiltration in a trephine biopsy (if done).
• No evidence of other B-cell proliferative disorders.
• No related organ or tissue impairment (no end organ damage, including bone lesions)^a

Asymptomatic (smoldering) myeloma.

• M-protein in serum  3 g/dL l, and/or:
• Bone marrow clonal plasma cells 10%.
• No related organ or tissue impairment (no end organ damage, including bone lesions) or symptoms.^a

Symptomatic multiple myeloma.

• M-protein in serum and/or urine.
• Bone marrow (clonal) plasma cells or plasmacytoma.
• Related organ or tissue impairment (end organ damage, including bone lesions).^a

Solitary plasmacytoma of bone.

• No M-protein in serum and/or urine.
• Single area of bone destruction due to clonal plasma cells.
• Bone marrow not consistent with multiple myeloma.
• Normal skeletal survey (and MRI of spine and pelvis if done).
• No related organ or tissue impairment (no end organ damage other than solitary bone lesion).^a

Non-secretory myeloma

• No M-protein in serum and/or urine with immunofixation.
• Bone marrow clonal plasmacytosis 10% or plasmacytoma.
• Related organ or tissue impairment (end organ damage, including bone lesions).^a

Extramedullary plasmacytoma.

• No M-protein in serum and/or urine.^a
• Extramedullary tumor of clonal plasma cells.
• Normal bone marrow.
• Normal skeletal survey.
• No related organ or tissue impairment (end organ damage including bone lesions).^a

Multiple solitary plasmacytomas (± recurrent).

• No M-protein in serum and/or urine.
• More than one localized area of bone destruction or extramedullary tumor of clonal plasma cells which may be recurrent.
• Normal bone marrow.
• Normal skeletal survey and MRI of spine and pelvis if done.
• No related organ or tissue impairment (no end organ damage other than the localized bone lesions)

Plasma cell leukemia

• Peripheral blood absolute plasma cell count of at least 2x10⁹/L and more than 20% plasma cells in the peripheral blood differential white cell count.

Note: ^aMyeloma-related organ or tissue impairment (end organ damage)

• Calcium levels increased.
• Renal insufficiency.
• Anemia.
• Bone lesions: lytic lesions or osteoporosis with compression fractures (MRI or CT may clarify).
• Other: symptomatic hyperviscosity, amyloidosis, recurrent bacterial infections (> 2 episodes in 12 months).
• CRAB (calcium, renal insufficiency, anemia or bone lesions).
• Some patients may have no symptoms but have related organ or tissue impairment.