Fine-needle aspiration biopsy diagnosis of gastrointestinal stromal tumors using morphology, immunocytochemistry, and mutational analysis of c-kit.
BACKGROUND
Differentiating gastrointestinal stromal tumors (GISTs) from other intramural mesenchymal tumors of the GI tract on fine-needle aspiration biopsies (FNABs) is difficult. Recent studies have shown that GISTs are immunophenotypically and genetically distinct. GISTs exhibit consistent immunohistochemical expression of CD-117 (KIT) and often express activating mutations of this protooncogene. The aim of the current study was to employ immunocytochemistry and mutational analysis of the c-kit gene to aid in the diagnosis of GISTs on FNAB.


METHODS
Five endoscopic ultrasound-guided FNABs of gastrointestinal spindle cell neoplasms performed at the Veterans Affairs Medical Center (VAMC) in Portland, Oregon, from 1998-1999 were reviewed. A panel of immunocytochemical stains was performed on each cellblock including CD-117 (KIT), smooth muscle actin (SMA), desmin, S-100, and CD34. Genomic DNA (gDNA) was extracted, and amplification of exons 9, 11, 13 and 17 of c-kit was performed by polymerase chain reaction (PCR) on CD-117 (KIT) and CD34 positive cases. Direct sequencing of amplicons identified the mutations.


RESULTS
Five patients were diagnosed with GISTs based on morphology and immunocytochemical positivity for CD-117 and CD34. PCR analysis of c-kit exon 11 revealed three cases with novel-sized PCR bands in addition to the expected wild-type-sized PCR product. Amplicons from these cases contained an in-frame deletion mutation. One of the two cases with wild-type-;sized exon 11 amplicons was found to be heterozygous for a point mutation producing an amino acid substitution (W557R). No mutations in exon 9, 11, 13, or 17 of c-kit were found in the remaining case.


CONCLUSIONS
Ancillary techniques such as immunocytochemistry and c-kit gene mutational analysis may aid in the diagnosis of GISTs on FNABs.
Rader
A E
AE
Department of Pathology, Oregon Health Sciences University, Portland, Oregon 97201-3098, USA. radera@ohsu.edu
Avery
A
A
Wait
C L
CL
McGreevey
L S
LS
Faigel
D
D
Heinrich
M C
MC
D000368:Aged; D000483:Alleles; D000595:Amino Acid Sequence; D001707:Biopsy, Needle; D002277:Carcinoma / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D004252:DNA Mutational Analysis; D004273:DNA, Neoplasm / Q000235:genetics; D005260:Female; D017353:Gene Deletion; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D017354:Point Mutation; D016133:Polymerase Chain Reaction; D019009:Proto-Oncogene Proteins c-kit / Q000235:genetics*; D013274:Stomach Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D017154:Stromal Cells / Q000473:pathology
D004273:DNA, Neoplasm; D019009:Proto-Oncogene Proteins c-kit