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WHO Classification of Tumours
Aggressive systemic mastocytosis
Tumours of haematopoietic and lymphoid tissues


Definition

Aggressive systemic mastocytosis (ASM) meets the criteria for systemic mastocytosis (SM). One or more "C" findings. No evidence of mast cell leukaemia. Usually without skin lesions.

Lymphadenopathic mastocytosis with eosinophilia
Progressive lymphadenopathy with peripheral blood eosinophilia, often with extensive bone involvement, and hepatosplenomegaly, but usually without skin lesions. Cases with rearrangement of PDGFRA are excluded.


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"B" findings
1. Bone marrow biopsy showing >30% infiltration by mast cells (focal, dense aggregates) and/or serum total tryptase level >20 ng/mL.
2. Signs of dysplasia or myeloproliferation, in non-mast cell lineage(s), but insufficient criteria for definitive diagnosis of a haematopoietic neoplasm (AHNMD), with normal or only slightly abnormal blood counts.
3. Hepatomegaly without impairment of liver function, and/or palpable splenomegaly without hypersplenism, and/or lymphadenopathy on palpation or imaging.

"C" findings
1. Bone marrow dysfunction manifested by one or more cytopenia (ANC <1.0x109/L, Hb <10 g/dL, or
platelets <100x109/L), but no obvious non-mast cell haematopoietic malignancy.
2. Palpable hepatomegaly with impairment of liver function, ascites and/or portal hypertension.
3. Skeletal involvement with large osteolytic lesions and/or pathological fractures.
4. Palpable splenomegaly with hypersplenism.
5. Malabsorption with weight loss due to GI mast cell infiltrates.