Systemic mastocytosis

Systemic mastocytosis
ICD-O-1 Morphology
9741/3: Malignant mastocytosis
Effective 1978 - 1991
ICD-O-2 Morphology
9741/3: Malignant mastocytosis
Effective 1992 - 2000
ICD-O-3 Morphology
9741/3: Malignant mastocytosis
Effective 2001 and later
for cases diagnosed 1978 and later
Primary Site(s)
Primary site must be bone marrow (C421)

Not Applicable
Module Rule
Alternate Names
Aggressive systemic mastocytosis
Lymphadenopathic (systemic) mastocytosis with eosinophilia
Malignant mastocytosis
Systemic mastocytosis with associated clonal hematological non-mast cell lineage disease
Accumulation of increased numbers of mast cells in tissues other than skin, such as the liver, spleen, bone marrow, stomach, and small intestines, with or without skin lesions. There are > 15% mast cells in aggregates in the bone marrow and/or other extracutaneous organs. The aggregates of neoplastic spindle-shaped mast cells are compact (not scattered throughout tissue).
Abstractor Notes
Bone marrow is almost always involved. Lymph nodes are rarely involved except for a variant of aggressive of systemic mastocytosis. The white and red pulp of the spleen may be involved. Involvement of liver may present with small granulomatoid foci of mast cells, but severe liver involvement is rare. It may frequently be suspected that the GI tract mucosa is involved based on symptoms, but it is rarely assessed morphologically.

There are several variants of SM:
1. [Indolent systemic mastocytosis (ISM) is NOT reportable; it includes subtypes bone marrow mastocytosis and smoldering systemic mastocytosis and would be coded as 9741/1 in the WHO classification; the mast cell burden is very low (<1% of nucleated bone marrow cells) and life expectancy is normal.]

2. Aggressive systemic mastocytosis (ASM) - Organomegaly and impaired organ function are usually present. There may be weight loss caused by malabsorption in the GI tract due to mast cell infiltrates, or skeletal involvement with large osteolytic lesions and/or pathologic fractures. There are usually no skin lesions. A type of ASM, lymphadenopathic mastocytosis with eosinophilia, features progressive lymphadenopathy with peripheral blood eosinophilia, often with extensive bone involvement and hepatosplenomegaly. Genetically cases classified as ASM have no PDGFRA rearrangement. Survival is a few years.

3. Systemic mastocytosis - associated clonal hematological non-mast-cell lineage disease (SM-AHNMD), a myeloid or lymphatic malignancy is diagnosed with the SM; CMML (9945/3) is the most common associated disease. The prognosis is usually dominated by the non-mast cell malignancy.
Definitive Diagnostic Methods
Bone marrow biopsy
Genetic testing
Histologic confirmation
Genetics Data
For ASM: no FDGFRA rearrangement
Somatic point mutation at codon 816 in kit receptor gene
Immunohistochemical markers anti-tryptase/chymase and anti-CD117
Blood thinners; anti-coagulant medications
Other therapy
Transformations to
There are no known transformations
Transformations from
There are no known transformations
Corresponding ICD-9 Codes
202.6 Malignant mast cell tumors
Corresponding ICD-10 Codes
C96.2 Malignant mast cell tumor
Corresponding ICD-10-CM Codes (U.S. only)
C96.2 Malignant mast cell tumor (effective October 01, 2015)
Signs and Symptoms
Abdominal pain
Bone pain
Gastrointestinal distress
Respiratory problems
Weight loss
Progression and Transformation
Epidemiology and Mortality
Age: primary second decade of life
Sex: no male or female predominance
Survival: patients with cutaneous involvement only follow indolent course and may have a normal life expectancy. Patients with no skin lesions and aggressive disease may survive only a few months