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. Author manuscript; available in PMC: 2021 May 1.
Published in final edited form as: Leuk Lymphoma. 2019 Dec 26;61(5):1075–1083. doi: 10.1080/10428194.2019.1703974

Table 1. The 2016 World Health Organization (WHO) classification for mastocytosis.

Categories Variants Diagnostic criteria Prognosis
Cutaneous mastocytosis (CM)

  • Urticaria pigmentosa (UP) ¼ Maculopapular cutaneous mastocytosis (MPCM)

  • Diffuse cutaneous mastocytosis (DCM

  • Mastocytoma of the skin

 No systemic involvement (most patients are children) Good
Systemic mastocytosis (SM)

  • Indolent systemic mastocytosis (ISM)

  • Smoldering SM (SSM)

  • SM with an associated hematologic neoplasm (SM-AHN)

  • Aggressive SM (ASM)

  • Mast cell leukemia (MCL)

  • No aB- and no bC-findings

  • Most patients are adults

  • 2 or more B-findings, no C-findings

  • SM criteria and WHO diagnostic criteria for AHN are fulfilled

  • Frequently associated with myeloid AHNs (MPN, MDS, MPN/MDS), rarely to lymphoid AHN

  • At least one C-finding

  • 20% MCs in the BM smears

  • <10% MCs in the PB smears

 Good


± Good

Depends on the type of SM and of the AHN



Poor
Very poor
Mast cell sarcoma (MCS)

  • Rare form of high-grade solid MC tumor

  • Very atypical MCs

 Very poor

ANC: absolute neutrophil count; BM: bone marrow; GI: gastro-intestinal; Hb: hemoglobin; MCs: mast cells; MDS: myelodysplastic syndrome; MPN: myeloproliferative neoplasm; PB: peripheral blood.

a

B-findings: (a) BM biopsy showing >30% infiltration by MCs (focal, dense aggregates) and/or serum total tryptase level >200 ng/mL; (b) signs of dysplasia or myeloproliferation, in non-MC lineage(s), but insufficient criteria for definitive diagnosis of a hematopoietic neoplasm (AHN), with normal or slightly abnormal blood counts; (c) hepatomegaly without impairment of liver function, and/or palpable splenomegaly without hypersplenism, and/or lymphadenopathy by palpation or imaging.

b

C-findings: (a) BM damage caused by infiltration of neoplastic MCs with consecutive cytopenia(s) (ANC <1.0 × 109/L, Hb <100 g/L, or platelets <100 × 109/L); (b) palpable hepatomegaly with SM-related impairment of liver function, ascites, and/or portal hypertension; (c) skeletal involvement with large (several cm) osteolytic lesions and/or pathological fractures caused by local MC infiltration (d) palpable splenomegaly with hypersplenism; (e) malabsorption with weight loss due to GI MC infiltrates.