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“Occult” mastocytosis with activating c-kit point mutation evolving into systemic mastocytosis associated with plasma cell myeloma and secondary amyloidosis
  1. K Sotlar1,
  2. W Saeger2,
  3. F Stellmacher3,
  4. J Stahmer4,
  5. S Jäckle4,
  6. P Valent5,
  7. H-P Horny3
  1. 1Institute of Pathology, University of Tübingen, Tübingen, Germany
  2. 2Marienkrankenhaus Hamburg, Hamburg, Germany
  3. 3Institute of Pathology, University of Lübeck, Lübeck, Germany
  4. 4Clinic of Internal Medicine, Reinbek Hospital St Adolf, Reinbek, Germany
  5. 5Department of Internal Medicine I (AKH), Division of Hematology and Hemostaseology, Medical University of Vienna, Vienna, Austria
  1. Correspondence to:
 Prof H-P Horny
 Institute of Pathology, University of Lübeck, Ratzeburger Allee 160, D-23538 Lübeck, Germany; horny{at}


A case of a 70-year-old man presenting with exsudative enteropathy due to light-chain-associated amyloidosis is reported. The diagnosis of systemic mastocytosis associated with IgG/λ plasma cell myeloma and secondary generalised amyloidosis was carried out by morphological evaluation of bone marrow biopsy. The c-kit point mutation D816Y was detected by molecular analysis. Two years before, a cystadenolymphoma of the left parotid gland had been removed. A moderate increase of loosely scattered spindle-shaped mast cells, a subpopulation of them expressing CD25, an antigen that is not expressed by normal or reactive mast cells, was shown by retrospective analysis carried out on an intraparotideal lymph node. The c-kit mutation D816Y was shown by the molecular analysis of the lymph node. In summary, the notion that systemic mastocytosis may very rarely be associated with B cell neoplasms and that neoplastic mast cell infiltrates may be obscured because of only a minimal increase of atypical mast cells, which are outnumbered by other non-neoplastic cells in the same tissue, is supported by this case. This finding was preliminarily termed “occult” mastocytosis.

  • AHNMD, associated clonal haematological non-mast cell lineage disease
  • PNA, peptide nucleic acid
  • SM-AHNMD, systemic mastocytosis associated clonal haematological non-mast cell lineage disease

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  • Funding: This study was in part supported by the Fortüne Förderprogramm, Universität Tübingen (F1461141), Tübingen, Germany.

  • Competing interests: None declared.