c-kit mutations in gastrointestinal stromal tumors occur preferentially in the spindle rather than in the epithelioid cell variant.
Gastrointestinal stromal tumors (GISTs) coexpress CD34 and the Kit tyrosine-kinase receptor (CD117). A subset of GISTs carry gain-of-function mutations of the c-kit proto-oncogene in its juxtamembrane domain. The relationship between the mutational status and histological as well as immunohistochemical features has not been assessed in detail. 36 GISTs and 14 other gastrointestinal mesenchymal tumors were investigated for their morphology and immunophenotype as well as for the presence of c-kit mutations. DNA was extracted from formalin-fixed, paraffin-embedded tissue. Exons 9, 11, 13, and 17 of c-kit were analyzed by SSCP. Bands with altered mobility were excised, reamplified, and sequenced. C-kit mutations in Exon 11 encoding the juxtamembrane domain were identified in 19 cases (52.8%), with deletions in 12 cases, insertions in 3 cases (2 of these as duplications), and point mutations in 4 cases. The mutations clustered between Codons 553 and 561, pinpointing the critical region for deregulated Kit receptor activation. In both Exons 9 and 13, single mutations could be identified, whereas no mutations were found in Exon 17. There were c-kit mutations in 66.6% of benign GISTs (14/21), 83.3% of the malignant (5/6), and 40% of the cases of intermediate malignancy (2/5). A low frequency of mutations in benign GISTs, as reported previously by other researchers, could not be observed in our panel. Interestingly, all GISTs with c-kit mutations displayed a spindle cell phenotype, whereas mutations were absent in all 7 tumors with an epithelioid component (P =.03). This finding suggests a relationship between c-kit mutation and histological subtype in GISTs.
Wardelmann
Eva
E
Department of Pathology, University of Bonn Medical Center, Bonn, Germany. eva.wardelmann@ukb.uni-bonn.de
Neidt
Iris
I
Bierhoff
Erhard
E
Speidel
Nicola
N
Manegold
Christoph
C
Fischer
Hans-Peter
HP
Pfeifer
Ulrich
U
Pietsch
Torsten
T
D000368:Aged; D000595:Amino Acid Sequence; D018952:Antigens, CD34 / Q000032:analysis; D001483:Base Sequence; D004252:DNA Mutational Analysis; D004273:DNA, Neoplasm / Q000737:chemistry / Q000235:genetics; D015622:Epithelioid Cells / Q000378:metabolism / Q000473:pathology*; D005260:Female; D005770:Gastrointestinal Neoplasms / Q000235:genetics / Q000473:pathology*; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D009154:Mutation; D020125:Mutation, Missense; D018807:Polymorphism, Single-Stranded Conformational; D000090063:Proto-Oncogene Mas; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000032:analysis; D019009:Proto-Oncogene Proteins c-kit / Q000032:analysis / Q000235:genetics*; D017384:Sequence Deletion; D017386:Sequence Homology, Amino Acid; D014746:Vimentin / Q000032:analysis
D018952:Antigens, CD34; D004273:DNA, Neoplasm; C000715470:MAS1 protein, human; D000090063:Proto-Oncogene Mas; D019253:Proto-Oncogene Proteins c-bcl-2; D014746:Vimentin; D019009:Proto-Oncogene Proteins c-kit