ABSTRACT
Mastocytosis comprises a spectrum of related diseases in which there is an increase in mast cells in one or more organs. It is classified into cutaneous and systemic. Cutaneous mastocytosis includes: urticaria pigmentosa, solitary mastocytoma, diffuse cutaneous mastocytosis and telangectasia macularis eruptive perstans. Systemic mastocytosis can be with or without cutaneous lesions. Juvenile xanthogranuloma is the most common non-Langerhans cell type of histiocytosis. Usually it is a self-limited disease. Xanthomas are group of infiltrates of foamy macrophages. They are often associated with hyperlipidemias although others may be normolipemic. Langerhans cell histiocytosis is a histioctytic disorder characterized by proliferation and accumulation of Langerhans cells into a variety of organs. Merkel cell carcinoma is a rare malignant primary cutaneous neoplasm with epithelial and neuroendocrine differentiation. The cell of origin remains unresolved.
