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Clinical calculator summary

Original NIH-Fletcher GIST Risk Criteria (2002)

Assigns one of four historical consensus groups from greatest primary tumor size and integer mitoses per historical 50 HPF.

Evidence-based context for fast calculator use

Purpose:
Reproduce the gap-free 2002 NIH-Fletcher size/mitosis classification without importing AFIP/Miettinen site-specific probabilities.
Population:
Adult sporadic, confirmed localized gastrointestinal GIST after adequate resection of an untreated, nonruptured primary tumor.
Factors:
Greatest tumor dimension, Integer mitotic count per historical 50 HPF, Resection and treatment context, Localized gastrointestinal primary, Absent rupture
Reference:
Fletcher CDM, et al. Hum Pathol. 2002;33(5):459-465. doi:10.1053/hupa.2002.123545.
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Original NIH-Fletcher GIST Risk Criteria (2002)

cm

Enter a positive raw size without rounding; exact 2, 5, and 10 cm boundaries are preserved.

Use only for a confirmed, localized, resected adult GIST without rupture, using an untreated specimen and an explicitly reported historical count per 50 HPF. Do not enter a count reported per 5 mm² only or when the counting basis is unknown.

Clinical Context & Background

This compatibility route implements the original 2002 NIH-Fletcher consensus criteria for gastrointestinal stromal tumor (GIST). It uses only the greatest tumor dimension and the pathologist-reported integer mitotic count per historical 50 high-power fields. The output is one of four historical consensus groups: very low, low, intermediate, or high.
The permanent slug contains “Miettinen,” but the visible identity and calculation are NIH-Fletcher only. The separate AFIP/Miettinen 2006 calculator uses anatomic site, calibrated 5 mm² mitotic assessment, and site-specific historical frequencies. Its engine and interpretation remain independent.
Use this route only for a confirmed primary localized gastrointestinal GIST after adequate resection, using an untreated specimen, absent tumor rupture, adult sporadic context, and assessment before adjuvant treatment. A historical per-50-HPF count must be explicitly reported. Counts expressed only per 5 mm², uncalibrated conversions, biopsy or inadequate specimens, unconfirmed mimics, recurrent or metastatic disease, post-neoadjuvant specimens, ruptured tumors, pediatric or syndromic GIST, and extragastrointestinal tumors are not classified.
This is a historical consensus risk-group interpreter. It does not provide a recurrence probability, classify a tumor as benign, calculate AFIP/Miettinen risk, stage GIST, determine surveillance, or recommend imatinib or another treatment.
Formula Logic
Gap-free original NIH-Fletcher decision table using raw greatest size in cm and integer mitoses per historical 50 HPF. No site, probability, rupture modifier, conversion, or treatment rule.

Reference Data

Historical groupGreatest tumor sizeMitoses per 50 HPF
Very low<2 cm≤5
Low2–5 cm≤5
Intermediate≤5 cm6–10
Intermediate>5–≤10 cm≤5
High>5 cm>5
High>10 cmAny
HighAny size>10

Clinical Workflow

Use, Interpret, And Continue The Patient Pathway

Expand for workflow guidance, limitations, examples, and related next steps.

When To Use

  • Use Original NIH-Fletcher GIST Risk Criteria (2002) when historical four-group NIH-Fletcher consensus classification using greatest primary GIST diameter and an integer mitotic count per historical 50 high-power fields.
  • Confirm that the patient, diagnosis, disease phase, and available inputs match the cited model before calculation.

How To Interpret

  • Interpret the displayed result using the calculator-specific formula and reference table, spanning Very low through High.
  • A boundary result should prompt input verification and clinical review rather than false precision.

What To Do Next

  • Confirm primary site, histology, stage, surgery status, systemic-treatment timing, and disease-specific guideline before applying the result.
  • Document the inputs, result, timing, and clinical context so the assessment can be reproduced.

Limitations

  • Do not transfer thresholds across colorectal, GIST, gastric, appendiceal, and other peritoneal malignancies.
  • The result supports clinician judgment and does not independently determine treatment.

Validated Population

patients with the specific gastrointestinal, stromal, colorectal, or peritoneal disease context described by the model

How to apply this result

For a representative case, verify Greatest tumor dimension, Mitotic count per historical 50 HPF, calculate the result, and confirm that its classification matches the highlighted reference band before continuing the disease-specific pathway.

GI, GIST & Peritoneal hubContinue to related calculators and clinical workflow resources.

Calculation verification history

Verified

  1. : Production browser revalidation

    • Three source-backed cases passed through visible production controls across Very low, Intermediate, and High NIH-Fletcher groups.
    • Raw size transitions immediately below 2 cm, above 5 cm, and above 10 cm produced the expected gap-free classifications.
    • No unexpected N/A, literal undefined value, stale control, unsupported gauge, or browser-console error was observed.
    Download latest production check (Excel)

    Case-level evidence is retained in validation/browser-revalidation/nih-gist-risk-miettinen-classification-2026-08-03.json.

  2. : Production browser validation

    • Ten source-backed cases were exercised on the public production route through visible browser controls; 10/10 case records passed their expected-versus-observed assertions across 11 visible submissions.
    • Overall browser status: failed-console. medium: Production emitted minified React error #418 during route loads/reloads used by this run.
    • Case-level inputs, expected and observed results, reset/repeat behavior, failure reproductions, and console evidence are retained in the production-browser evidence record.

    Case-level production evidence is retained in validation/browser-production/nih-gist-risk-miettinen-classification.json.

  3. : Public form simplified

    • Combined eight diagnosis, specimen, extent, treatment, rupture, site, patient, and mitotic-basis questions into one early applicability confirmation.
    • Preserved the only two historical classification determinants: raw greatest tumor dimension and integer mitotic count per historical 50 HPF.
    • The compact adapter projects confirmed applicability into the unchanged strict ten-key engine; declined or uncertain applicability stops before pathology entry.

  4. : Model identity corrected

    • Preserved the permanent compatibility route while replacing the mixed NIH/Miettinen visible identity with the original NIH-Fletcher GIST risk criteria (2002).
    • Kept the verified AFIP/Miettinen 2006 site-dependent table independent and clinically unchanged.

  5. : Strict input and applicability contract added

    • Added an immutable exact ten-own-key contract covering raw size, integer historical 50-HPF mitoses, diagnosis, specimen, extent, treatment, rupture, site, and adult sporadic context.
    • Malformed values are invalid; unknown facts are incomplete; explicit excluded populations and 5 mm²-only counts are outside scope.

  6. : Calculation and interpretation corrected

    • Implemented gap-free high-risk precedence and exact 2, 5, and 10 cm and 5, 6, 10, and 11 mitosis boundaries without rounding or fallthrough.
    • Removed site-specific probabilities, benign wording, imatinib and surveillance guidance, and any claim that 50 HPF is interchangeable with 5 mm².

  7. : Full validation completed

    • 768/768 independent deterministic assertions passed across source identity, matrix and boundaries, malformed and applicability states, AFIP isolation, trace, UI, registry, history, and report checks.
    • This is software implementation verification against locked public definitions, not prospective or independent clinical validation.

Verification confirms the calculator implementation against the cited model; it is not independent clinical validation, regulatory approval, or medical advice.

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AFIP/Miettinen GIST Risk Table (2006)

Frequently Asked Questions

Is this the AFIP/Miettinen GIST table?

No. This route is the original 2002 NIH-Fletcher four-group classification using size and mitoses per historical 50 HPF only. AFIP/Miettinen is a separate site-dependent 2006 table with calibrated 5 mm² counting and historical percentages.

Can a mitotic count per 5 mm² be entered?

No. This source lock requires an explicitly reported historical 50-HPF count. The calculator does not assume that 50 HPF equals 5 mm² and does not convert between bases.

Does a historical high-risk group determine imatinib or surveillance?

No. The result is a historical consensus group, not a treatment recommendation, individualized probability, current preferred risk model, or substitute for contemporary specialist assessment.

Evidence-based oncology decision support. Verify with clinical guidelines.