"Occult" mastocytosis with activating c-kit point mutation evolving into systemic mastocytosis associated with plasma cell myeloma and secondary amyloidosis.
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/lambda 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.
Sotlar
K
K
Institute of Pathology, University of Tübingen, Tübingen, Germany.
Saeger
W
W
Stellmacher
F
F
Stahmer
J
J
Jäckle
S
S
Valent
P
P
Horny
H-P
HP
D000368:Aged; D000686:Amyloidosis / Q000209:etiology* / Q000473:pathology; D018450:Disease Progression; D006801:Humans; D007410:Intestinal Diseases / Q000209:etiology / Q000473:pathology; D008297:Male; D008415:Mastocytosis / Q000150:complications / Q000235:genetics*; D034721:Mastocytosis, Systemic / Q000150:complications / Q000235:genetics; D009101:Multiple Myeloma / Q000150:complications*; D017354:Point Mutation; D019009:Proto-Oncogene Proteins c-kit / Q000235:genetics*
D019009:Proto-Oncogene Proteins c-kit