IgM Monoclonal Gammopathy of Undetermined Significance, Not Otherwise Specified

**Semantic type:** Neoplastic Process

**Definition:** A subtype of IgM monoclonal gammopathy of undetermined significance that includes cases associated with MYD88 mutation and cases associated with the presence of monoclonal B-lymphocytes without the presence of abnormal lymphoplasmacytic aggregates that are diagnostic of lymphoplasmacytic lymphoma or other small B-lymphocytic neoplasms.

**Synonyms:** - IgM MGUS, NOS - IgM MGUS, Not Otherwise Specified - IgM Monoclonal Gammopathy of Undetermined Significance, NOS