GIST Flashcards
Histological classification of GIST
spindle cell (70%) epithelioid type (20%) mixed (10%)
c-KIT
proto-oncogene
mutation -> KIT receptor overactivity -> unregulated cell growth and malignant transformation
PDGFRA
Platelet derived growth factor receptor alpha
Gene encoding related receptor tyrosine kinase
Wild type GIST
exhibit no detectable KIT or PDGFRA
Pathological diagnosis of GIST
1) morphology
2) immunohistochemical staining (CD 117, CD 34)
3) Gene mutation analysis (KIT, PDGFRA)
Common sites for GIST
stomach 60% small bowel 30% duodenum 5% colorectal <5% eso and appendix < 1%
Risk factors for GIST
1) mitotic index
2) size
3) site of origin
Other risk factors:
tumor grade
rupture
c-kit status
Prognostic models for GIST
AFIP
NIH risk stratification scheme
AJCC
Memorial Sloan Kettering nomogram
NIH risk stratification scheme
Risk of 10 year recurrence based on: tumor size (cm), mitotic index (per 50 HPFs), primary tumor site
AFIP (Armed Forces Institute of Pathology) prognostic model
Rate of progression-free survival based on: mitotic rate tumour size primary site completeness of resection
MSK (Memorial Sloan Kettering) nomogram
online GIST nomogram to predict postoperative recurrence-free survival:
tumor size
tumor site
mitotic index
Is there an ideal margin?
*Evidence
R0 or R1 better than R2
Retrospective multicentere series show lack fo difference in RFS between R0 and R1
What is imatinib?
Tyrosine kinase receptor inhibitor -> inhibits cell proliferation and promotion of apoptosis
Indication for surgical resection of GIST
> 2cm
Symptomatic
Suspicious EUS features
EUS high risk features for GIST
irregular border ulceration echogenic foci heterogeneity ulceration
