GIST Risk Stratification Calculator

icon GIST Risk Stratification Calculator

1. Microscope Calibration

? The value printed on your eyepiece (e.g. 20, 22, 25). Used to calculate the exact field diameter and area for your microscope.
Printed on eyepiece (e.g., 22)
? The magnification setting of the objective lens used during mitotic counting (typically 40x).
Typically 40x for mitoses
Field diameter / single field area: 0.55 mm / 0.238 mm²
Fields needed to survey 5 mm²: 21.0 HPFs

2. Tumor Parameters

? Anatomic origin of the GIST. Risk differs substantially by site — gastric GISTs behave less aggressively than small bowel or rectal GISTs of the same size and mitotic rate.
? Largest diameter of the tumor in centimeters.
? Mitotic figures counted across a total tumor area of 5 mm² (in the most mitotically active regions), per the WHO/Miettinen & Lasota / NCCN scheme. This is the current standard, since 50 HPF varies in actual area between microscopes depending on eyepiece field number.
Count across the 21.0 HPFs shown above to total 5 mm²
? Spontaneous or intraoperative tumor rupture. Under the modified NIH (Joensuu) criteria, rupture alone places a GIST in the high-risk category regardless of size or mitotic rate.
Size category: —
Mitotic index category: —
Est. rate of progressive disease: —
Risk Category (Miettinen & Lasota / NCCN)
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Based on the Miettinen & Lasota (AFIP) risk table as adapted by the WHO/NCCN, which stratifies GIST risk of progressive disease by primary site, tumor size, and mitotic rate (mitoses per 5 mm² of tumor area). Tumor rupture is incorporated per the modified NIH (Joensuu) consensus criteria. This tool is a calculation aid only and does not replace professional pathological or oncologic judgment.