Canterbury DHB
SM is typically associated with dense, multifocal mast cell infiltrates of the bone marrow. Malignant mast cells often show atypia (spindle-shape) and may be hypogranular, which makes them difficult to identify in H&E sections. Special stains are necessary to identify mast cells (tryptase) and malignant mast cells (CD2 and CD25 positive).
For criteria of SM, see Valent P (2016),2 table 1.
C-kit mutation analysis is required to determine whether patients are likely to respond to imatinib. Patients with wild-type KIT, or those with other mutations (such as K509I or F522C) may be sensitive to imatinib. However, over 80% of patients with SM have a KITC816V mutation and do not respond to imatinib.
For an algorithm for diagnosing and classifying SM, see Pardanani A, Tefferi A (2010),5 figure 1.
Topic Code: 8062