title: Diagnosis of mastocytosis: general histopathological aspects, morphological criteria, and immunohistochemical findings.
abstract: An increase in mast cell (MC) numbers in hemopoietic tissues may be associated with (a) primary neoplastic MC disease (mastocytosis); (b) non-mast cell lineage myelogenous disorders (myelodysplastic or myeloproliferative syndromes and myeloid leukemias); or (c) reactive, i.e. non-clonal states (MC hyperplasia and reactive mastocytosis). However, the histologic discrimination between hyperplastic states and neoplastic MC proliferative disorders is sometimes very difficult. MC hyperplasia is characterized by a diffuse increase in mature, round or spindle-shaped, metachromatic MC that are loosely scattered throughout the tissue and do not form dense focal infiltrates, even in states of marked hyperplasia. However, loosely scattered MC are also a prominent feature of many cases of myelodysplastic syndromes and acute leukemia involving the MC lineage. In contrast, the demonstration of dense, focal and/or diffuse MC infiltrates can be regarded as indicative of primary MC disease/mastocytosis. In addition to the highly diagnostic focal MC infiltrates, mastocytosis may also present with a predominantly diffuse or a mixed (diffuse and focal) infiltration pattern. The relatively rare diffuse pattern is usually dominated by atypical, often hypogranulated or even non-metachromatic MC and is associated with the aggressive or frankly malignant subtypes of systemic mastocytosis and MC leukemia. Although the demonstration of MC infiltrates in Giemsa-stained tissue sections is still very important for the diagnosis of mastocytosis, immunohistochemical techniques using antibodies against MC-associated antigens such as tryptase or c-kit (CD117) are essential for the identification of highly atypical, hypogranulated MC, especially in MC leukemia, and for the detection of small and even minute MC infiltrates.
authors.affiliation: Institute of Pathology, Medical University of Lübeck, Ratzeburger Allee 160, D-23538 Lübeck, Germany. horny@patho.mu-luebeck.de
authors.forename: H P
authors.initials: HP
authors.lastname: Horny
authors.forename: P
authors.initials: P
authors.lastname: Valent
mesh_terms: D000328:Adult; D015415:Biomarkers; D001853:Bone Marrow / Q000473:pathology; D002265:Carboxylic Ester Hydrolases / Q000032:analysis; D002452:Cell Count; D019070:Cell Lineage; D053818:Chymases; D003937:Diagnosis, Differential; D004064:Digestive System / Q000473:pathology; D005188:False Negative Reactions; D006801:Humans; D006965:Hyperplasia; D007946:Leukemia, Mast-Cell / Q000175:diagnosis / Q000473:pathology; D008221:Lymphoid Tissue / Q000473:pathology; D008407:Mast Cells / Q000737:chemistry / Q000473:pathology*; D008415:Mastocytosis / Q000175:diagnosis* / Q000378:metabolism / Q000473:pathology; D009190:Myelodysplastic Syndromes / Q000175:diagnosis / Q000473:pathology; D022423:Myeloid Cells / Q000473:pathology; D019009:Proto-Oncogene Proteins c-kit / Q000032:analysis; D012680:Sensitivity and Specificity; D012697:Serine Endopeptidases / Q000032:analysis; D013194:Staining and Labeling; D053802:Tryptases
chemical_list: D015415:Biomarkers; D019009:Proto-Oncogene Proteins c-kit; D002265:Carboxylic Ester Hydrolases; C019873:chloroacetate esterase; D012697:Serine Endopeptidases; D053818:Chymases; D053802:Tryptases