A mast cell neoplasm that is characterized by collections of mast cells with a single or multiple (usually five or fewer individual) orange-brown to red-brown plaques or nodules ranging from 0.5 to 3.5 cm in diameter.
A bone marrow cancer that is formed of any one of the bone marrow cells belonging to the granulocytic (neutrophil, eosinophil, basophil), monocytic/macrophage, erythroid, megakaryocytic and mast cell lineages.