Table 3. B and C findings in systemic mastocytosis (SM).

BM: Bone marrow, ANC: Absolute neutrophil count

B findings	C findings
1. High mast cell burden shown on BM biopsy: >30% infiltration of cellularity by mast cells (focal, dense aggregates) and serum total tryptase level > 200 ng/mL	1. Bone marrow dysfunction caused by neoplastic mast cell infiltration, manifested by ≥1 cytopenia(s) (ANC <1.0 × 109/L, Hgb <10 g/dL, and/or platelet count <100 × 109/L).
2. High mast cell burden shown on BM biopsy: >30% infiltration of cellularity by mast cells (focal, dense aggregates) and serum total tryptase level > 200 ng/mL	2. Palpable hepatomegaly with impairment of liver function, ascites and/or portal hypertension.
3. Signs of dysplasia or myeloproliferation, in non-mast cell lineage(s), but insufficient criteria for definitive diagnosis of an associated hematological neoplasm (AHN), with normal or only slightly abnormal blood counts.	3. Skeletal involvement with large osteolytic lesions with/without pathological fractures (pathological fractures caused by osteoporosis do not qualify as a “C” finding.
4. Hepatomegaly without impairment of liver function, palpable splenomegaly without hypersplenism, and/or lymphadenopathy on palpation or imaging.	4. Palpable splenomegaly with hypersplenism.
	5. Malabsorption with weight loss due to gastrointestinal mast cell infiltrates.