Hi Nancy - Until someone can get back to you who has experience with this diagnosis here is what I found. My personal experience with blood cancer has been with non-Hodgkins Lymphoma
Hope the following info helps
....Systemic mastocytosis is considered a type of blood cancer with two main types.
Two Types of Systemic Mastocytosis
Indolent systemic mastocytosis (ISM): This type is slow moving and in the early stages. Mast cells build up in the tissues and organs, but the buildup of cells does not cause problems in the organs.
Advanced systemic mastocytosis (AdvSM): Mast cells build up in organs and tissues and cause problems in the organs they invade. ADvSM has three subtypes:
Aggressive systemic mastocytosis (ASM)
Systemic mastocytosis with associated hematologic neoplasm (SM-AHN)
Mast cell leukemia (MCL)
Your doctor can answer any questions you may have about each type
... Dennis (Blood-Cancer.com TEAM)