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Case 120 - Discussion

Uploaded: 2010-07-14, Updated: 2011-02-18

 

Mastocytosis

  • Classification:

    • Cutaneous mastocytosis: mostly urticaria pigmentosa (UP) in children. Less commonly telangiectasia macularis eruptiva perstans (TMEP) in adults.
    • Indolent systemic mastocytosis
    • Systemic mastocytosis with associated clonal hemtological non-mast-cell lineage diease
    • Aggressive systemic mastocytosis
    • Mast cell leukemia
    • Mast cell sarcoma
    • Extracutaneous mastocytoma
  • Criteria for systemic mastocytosis: one major and one minor or at least three criteria
    • Major criteria: multifocal dense infiltrates of mast cells of at least 15 cells
    • Minor criteria:
      • > 25% mast cells are spindle, atypical or immature
      • Condon 816 mutation of c-Kit
      • CD2+ and/or CD25+
      • Serum tryptase > 25 ng/ml
  • Morphology

    • Cohesive aggregates of mast cells with short spindle nuclei, blunt ends, open chromatin. Cytoplasm is pale pink and blue.

    • Lymphoid aggregates

    • Mixed eosinophils

  • Special stains

    • CAE (naphthol-ASD-chloroacetate esterase) +

    • Giemsa or toluidine blue

  • Immunostains: CD117+, CD2+, CD25+, tryptase+, chymase+, CD45+, CD68+, CD14-, CD16-

  • Genetics: point mutation of c-Kit, mostly codon 816 in the tyrosine kinase domain.

Reference: Swerdlow, S.H., Campo, E., Harris, N.L., Jaffe, E.S., Pileri, S.A., Stein, H., Thiele, J., Vardiman, J.W. WHO Classification of Tumours of Haematopoietic and Lymphoid Tissues, Fourth Edition. 2008.