Chapter 1 – Pathology and Classification
Classification of soft tissue sarcomas: histological grading
Histological grading of STS (Grade 1, 2 or 3) is performed according to FNCLCC.
Three parameters are evaluated: tumour differentiation, mitotic count and tumour necrosis.
The main value of grading is to predict the probability of distant metastases and overall survival (OS). It does not predict local recurrence.
FNCLCC grading is less informative in RMS, Ewing sarcoma, ASPS, epithelioid sarcoma and clear cell sarcoma; these are by definition high grade.
Epithelioid sarcoma is by definition high grade. Note the area of necrosis on the left.
In myxoid liposarcoma, the percentage of hypercellular round cell component determines the grade: >5% is considered high grade.
For adult patients with localised STS, metastasis-free survival correlates with histological grade (from the French Sarcoma Group database).
Histological grading cannot be performed after neoadjuvant therapy.
Histological grading is not a substitute for a histological diagnosis.
REVISION QUESTIONS
1. Which criteria are used for histological grading?
2. For which tumours is FNCLCC grading not applicable?
3. What is the purpose of histological grading?
WHO classification of STS: use of immunohistochemistry WHO classification of bone sarcomas -1
