**Light-chain monoclonal gammopathy of undetermined significance**

Abnormal free light chain (FLC) ratio (<0.26 or >1.65).

Increased level of the appropriate involved light chain (increased κ FLC in patients with a ratio >1.65 and increased λ FLC in patients with a ratio).

No immunoglobulin heavy chain expression on immunofixation.

The absence of end-organ damage such as hypercalcemia, renal insufficiency, anemia, and bone lesions (CRAB) or amyloidosis that can be attributed to the plasma cell proliferative disorder Clonal bone marrow plasma cells<10%.

Urinary monoclonal protein <500 mg/24 h.

### **Solitary plasmacytoma**

Biopsy-proven solitary lesion of bone or soft tissue with evidence of clonal plasma cells.

Normal bone marrow with no evidence of clonal plasma cells.

Normal skeletal survey and *magnetic resonance imaging* (MRI) or Computed tomography (CT) of spine and pelvis (except for the primary solitary lesion) Absence of end-organ damage such as hypercalcaemia, renal insufficiency, anemia, or bone lesions (CRAB) that can be attributed to a lymphoplasma cell proliferative disorder.
