ABSTRACT
Mastocytosis is a heterogeneous group of bone marrow (BM)-derived disorders characterized by proliferation of the clonally transformed mast cells, often associated with somatic activating point mutations within KIT, and a broad spectrum of clinical and morphologic features ranging from self-limiting benign disorders (i.e., juvenile cutaneous mastocytosis (CM) or urticaria pigmentosa (UP)) to highly aggressive neoplasms like mast cell leukemia [1–5]. The symptoms observed in mastocytosis are related to the spontaneous or triggered release of mast cell mediators or due to consequences of pathological accumulation of mast cells in tissues. Basically, mastocytosis can be divided into two main subtypes: CM and systemic mastocytosis (SM), the latter mainly involving the BM. The WHO divides SM into several major subtypes (Table 33.1): CM, indolent SM (ISM), SM with an associated clonal hematological non-mast-cell disorder (SM-AHN), aggressive SM (ASM), mast cell leukemia, mast cell sarcoma, and extracutaneous mastocytoma [6–10]. CM can be divided into four different clinical variants: UP, solitary mastocytoma, diffuse CM, and telangiectasia macularis eruptiva perstans [11].
