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Bone marrow - nonneoplastic


Mast cells

Reviewers: Dragos Luca, M.D. (see Reviewers page)
Revised: 16 October 2012, last major update August 2012
Copyright: (c) 2001-2012, PathologyOutlines.com, Inc.


● Part of the immune system; functionally and structurally closely related to basophils but current evidence indicates that immediate precursors are different
● Arise from same progenitor cell population as neutrophils, eosinophils, basophils and monocytes (CD34+, c-Kit+, CD13+)
● Production driven by stem cell factor (c-Kit ligand), thrombopoietin, flt3 ligand and IL6
● Mast cells leave bone marrow and circulate in immature form, mature at tissue site (basophils mature in bone marrow)
● Play a central role in allergic reactions through IgE receptor mediated responses; granules are rich in histamine and heparin
● Also have protective role in wound healing, defense against pathogens
● Stem cell factor is crucial for their development, proliferation and maturation (Immunol Res 2006;34:97)

Micro description

● Rare in normal marrow, usually concentrated within particles on aspirate smears and perivascular on biopsy sections
● Larger (up to 100%) than basophils with irregular, elongated spindle shapes and cytoplasmic extensions
● Cytoplasm is packed with basophilic granules that may obscure nuclear margin; nucleus is round and single (lobated in basophils)

Micro images

Mast cells

Spindle mast cell

Mast cells in kidney (various images)

Purple (metachromatic) granules with toluidine blue

Positive stains

● Mast cell tryptase, Giemsa stain, Leder stain (chloroacetate esterase), toluidine / methylene blue (granules stain purple - metachromatic) and microphthalmia transcription factor
● CD13 (immature and neoplastic mast cells), CD29, CD33, CD34, CD41, CD43, CD45, CD50, CD52, CD61, CD63, CD68, CD88 (J Allergy Clin Immunol 2005;115:1162), CD117, CD172a and CD203c
● Abnormal (immature / neoplastic) mast cells also express CD2 and/or CD25, unlike normal ones

Negative stains

● CD1-CD8, CD10-CD17, CD19-CD24, CD25 (non-neoplastic mast cells) and CD38

Electron microscopy images

Various images

Mast cells in secretory meningioma

Additional references

Wikipedia, Blood 1989;73:1778

End of Bone Marrow - nonneoplastic > Normal > Mast cells

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