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Clinical calculator summary

FNCLCC Soft Tissue Sarcoma Grade

A three-component histologic grade based on differentiation, mitotic count, and necrosis.

Evidence-based context for fast calculator use

Purpose:
Reproduce the source-defined FNCLCC grade from an appropriately sampled adult soft-tissue sarcoma.
Population:
Appropriately sampled adult soft-tissue sarcoma for which FNCLCC grading is applicable.
Factors:
Tumor differentiation, Corrected mitotic count, Tumor necrosis, Histologic applicability, Representative sampling
Reference:
Trojani et al. 1984; Guillou et al. 1997; CAP Soft Tissue Protocol v4.2.0.0.
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FNCLCC Grade (Soft Tissue Sarcoma)

Clinical Context & Background

The FNCLCC system assigns adult soft-tissue sarcoma histologic grade using tumor differentiation, mitotic count, and tumor necrosis. The mitotic category should use an unrounded count corrected for the microscope field area; CAP recommends counting per 1 mm2 or applying field-area correction.
Use representative pathology material. Limited biopsies may underestimate grade, and previously treated tumors require caution. Do not assign FNCLCC grade to alveolar soft-part sarcoma, clear-cell sarcoma, epithelioid sarcoma, extraskeletal myxoid chondrosarcoma, low-grade fibromyxoid sarcoma, sclerosing epithelioid fibrosarcoma, or angiosarcoma. Prognostic significance is uncertain in MPNST; use a dedicated risk model for solitary fibrous tumor.
FNCLCC grade is not AJCC stage, an individualized prognosis, or a treatment-selection rule. Integrate it with histologic subtype, size, depth, site, margins, imaging, and multidisciplinary sarcoma review.
Primary Source EvidenceTrojani M, et al. Int J Cancer. 1984;33(1):37-42. Guillou L, et al. J Clin Oncol. 1997;15(1):350-362. CAP Protocol for Soft Tissue Tumors, version 4.2.0.0.
Formula Logic
FNCLCC total = differentiation (1-3) + mitotic score (1-3) + tumor necrosis (0-2). Totals 2-3 = Grade 1, 4-5 = Grade 2, and 6-8 = Grade 3.

Reference Data

Total scoreFNCLCC grade
2-3Grade 1
4-5Grade 2
6-8Grade 3

Clinical Workflow

Use, Interpret, And Continue The Patient Pathway

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

When To Use

  • Use after an experienced pathologist has assigned all three components from representative adult soft-tissue sarcoma tissue.
  • Confirm that the histologic subtype is suitable for FNCLCC grading before calculating.

How To Interpret

  • Add differentiation (1-3), mitotic score (1-3), and necrosis (0-2).
  • Totals 2-3 are Grade 1, 4-5 Grade 2, and 6-8 Grade 3.

What To Do Next

  • Document the three component scores and sampling context.
  • Integrate grade with subtype, size, depth, site, margins, imaging, stage, and specialist sarcoma review.

Limitations

  • Limited biopsy may underestimate grade; previously treated tumors require caution.
  • Do not assign FNCLCC grade to alveolar soft-part sarcoma, clear-cell sarcoma, epithelioid sarcoma, extraskeletal myxoid chondrosarcoma, low-grade fibromyxoid sarcoma, sclerosing epithelioid fibrosarcoma, or angiosarcoma. Prognostic significance is uncertain in MPNST; use a dedicated risk model for solitary fibrous tumor.
  • The result is not a standalone prognosis or treatment recommendation.

Validated Population

Adult soft-tissue sarcoma with adequate representative pathology material and an FNCLCC-applicable histology.

Grade 2 example

Differentiation 2, mitotic score 2 (10-19/10 HPF), and necrosis 1 (<50%) total 5, which maps to Grade 2.

Enneking bone sarcoma stagingSeparate staging context for bone sarcoma.Mirels bone metastasis scoreSeparate fracture-risk assessment for metastatic bone lesions.Tokuhashi spine metastases prognosisSeparate prognostic context for spinal metastases.

Calculation verification history

Verified

  1. : Production browser revalidation

    • Five source-backed FNCLCC cases were exercised on the public production route through visible controls; 5/5 expected totals and grades matched across totals 2, 3, 4, 5, and 8.
    • No unexpected N/A, literal undefined value, stale control, or browser-console error was observed.
    Download latest production check (Excel)

    Case-level evidence is retained in validation/browser-revalidation/fnclcc-sacroma-grading-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/fnclcc-sacroma-grading.json.

  3. : Full validation test

    • 128/128 source-rule, boundary, malformed-input, UI, trace, scope, immutability, report, registry, and isolation checks passed.
    • No registered master panel calculates FNCLCC; no panel receives inherited verification.

  4. : Input-contract and scope correction

    • Removed preselected defaults and numeric coercion; all three exact pathology categories are now required and missing, extra, malformed, or unsupported values are rejected.
    • Added complete differentiation wording, corrected mitotic field-area guidance, applicability exclusions, sampling cautions, and non-prescriptive interpretation.

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

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Frequently Asked Questions

Does FNCLCC grade replace sarcoma staging?

No. It is a histologic grade and must be integrated with tumor size, depth, site, margins, nodal or metastatic disease, imaging, and multidisciplinary review.

How should mitoses be counted?

Use the unrounded, field-area-corrected count. CAP recommends counting per 1 mm2 or correcting the microscope field area before assigning the 0-9, 10-19, or 20-or-more per 10 HPF category.

Can every soft-tissue sarcoma receive an FNCLCC grade?

No. Several histologies are unsuitable, angiosarcoma should not be graded this way, MPNST has uncertain prognostic significance, and solitary fibrous tumor requires its dedicated risk model.

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