WHO classification of mastocytosis
| Classification . |
|---|
| 1. CM |
| a. UP/MPCM |
| b. Diffuse CM |
| c. Solitary mastocytoma of skin |
| 2. ISM: Meets criteria for SM.* No C findings.* No evidence of associated clonal hematological nonmast cell lineage disease. |
| a. Smoldering SM†: As above (ISM) but with 2 or more B findings, and no C findings.* |
| b. Isolated BM mastocytosis†: As above (ISM) with BM involvement but without skin involvement. |
| 3. SM with an associated SM-AHNMD: Meets criteria for SM and criteria for AHNMD as a distinct entity per the WHO classification |
| 4. ASM: Meets criteria for SM. One or more C findings.* No evidence of mast cell leukemia. |
| a. Lymphadenopathic mastocytosis with eosinophilia |
| 5. MCL: Meets criteria for SM. BM biopsy shows a diffuse infiltration, usually compact, by atypical immature mast cells. BM aspirate smears show ≥20% mast cells. In typical MCL, mast cells account for ≥10% of peripheral blood white cells. Rare variant: aleukemic MCL. |
| 6. MCS: Unifocal mast cell tumor. No evidence of SM. Destructive growth pattern. High-grade cytology. |
| 7. Extracutaneous mastocytoma: Unifocal mast cell tumor. No evidence of SM. No skin lesions. Nondestructive growth pattern. Low-grade cytology. |
| Classification . |
|---|
| 1. CM |
| a. UP/MPCM |
| b. Diffuse CM |
| c. Solitary mastocytoma of skin |
| 2. ISM: Meets criteria for SM.* No C findings.* No evidence of associated clonal hematological nonmast cell lineage disease. |
| a. Smoldering SM†: As above (ISM) but with 2 or more B findings, and no C findings.* |
| b. Isolated BM mastocytosis†: As above (ISM) with BM involvement but without skin involvement. |
| 3. SM with an associated SM-AHNMD: Meets criteria for SM and criteria for AHNMD as a distinct entity per the WHO classification |
| 4. ASM: Meets criteria for SM. One or more C findings.* No evidence of mast cell leukemia. |
| a. Lymphadenopathic mastocytosis with eosinophilia |
| 5. MCL: Meets criteria for SM. BM biopsy shows a diffuse infiltration, usually compact, by atypical immature mast cells. BM aspirate smears show ≥20% mast cells. In typical MCL, mast cells account for ≥10% of peripheral blood white cells. Rare variant: aleukemic MCL. |
| 6. MCS: Unifocal mast cell tumor. No evidence of SM. Destructive growth pattern. High-grade cytology. |
| 7. Extracutaneous mastocytoma: Unifocal mast cell tumor. No evidence of SM. No skin lesions. Nondestructive growth pattern. Low-grade cytology. |
ASM, aggressive systemic mastocytosis; MCL, mast cell leukemia; MCS, mast cell sarcoma; UP, urticaria pigmentosa; AHNMD, associated clonal hematological nonmast cell lineage disease.
See Table 2 for diagnostic criteria for systemic mastocytosis and definition of B and C findings.
Provisional categories.