Indolent systemic mastocytosis

Bone marrow mastocytosis

ISM

In indolent systemic mastocytosis (ISM), the mast cell burden is usually low and skin lesions are found in most patients. For cases that fulfill the criteria for indolent systemic mastocytosis and also present with one B finding, the diagnosis remains indolent systemic mastocytosis. However, if two or more B findings are detected, the diagnosis changes to smoldering systemic mastocytosis.

Bone marrow mastocytosis is a subtype of indolent systemic mastocytosis, the burden of neoplastic mast cells is usually low, and serum tryptase levels are often normal or nearly normal.

The criteria for ISM include:
1. No C findings (organ involvement)
2. No evidence of an associated hematological neoplasm
3. Low mast cell burden
4. Skin lesions are almost invariably present

The criteria for Bone marrow mastocytosis:
Indolent systemic mastocytosis, but with bone marrow involvement and no skin lesions

238.5 Neoplasm of uncertain behavior of histiocytic and mast cells

D47.0 Histiocytic and mast cell tumors of uncertain and unknown behavior

Swerdlow SH, Campo E, Harris NL, Jaffe ES, Pileri SA, Stein H, Thiele J (Eds):
WHO Classification of Tumours of Haematopoietic and Lymphoid Tissues (Revised 4th edition)
IARC: Lyon 2017
Section: Mastocytosis
Pages: 66

International Classification of Diseases for Oncology, Third Edition, Second Revision. Geneva: World Health Organization, 2020.
Section: ICD-O-3.2 (2020) Morphological Codes
Pages: http://www.iacr.com.fr/index.php?option=com_content&view=category&layout=blog&id=100&Itemid=577