FNCLCC (Fédération Nationale des Centres de Lutte Contre le Cancer)

The FNCLCC (Fédération Nationale des Centres de Lutte Contre le Cancer) is the most common grading system doctors use to evaluate soft tissue sarcomas, which are cancers that start in tissues like muscles, fat, or blood vessels. This grading system helps doctors assess how aggressive (fast-growing) the tumour is, guiding treatment decisions and helping predict outcomes.

How is the FNCLCC system used?

The FNCLCC grading system helps doctors determine how likely a soft tissue sarcoma is to grow quickly, spread to other body parts, and return after treatment. It classifies the tumour into different grades, guiding treatment decisions such as surgery, radiation, or chemotherapy.

What are the components of the FNCLCC system and how are they assessed?

The FNCLCC system evaluates soft tissue sarcomas based on three components:

1. Tumour differentiation: Differentiation refers to how much the cancer cells look like normal cells. Well differentiated tumours look more like normal cells and are given a lower score. Poorly differentiated tumours look very different from normal cells and receive a higher score.Here is a list of common soft tissue sarcoma types and their differentiation scores:

1. 1. Atypical lipomatous tumour / well differentiated liposarcoma: 1
   2. Well differentiated leiomyosarcoma: 1
   3. Malignant neurofibroma: 1
   4. Well differentiated fibrosarcoma: 1
   5. Myxoid liposarcoma: 2
   6. Conventional leiomyosarcoma: 2
   7. Conventional fibrosarcoma: 2
   8. Myxofibrosarcoma: 2
   9. High grade myxoid liposarcoma: 3
   10. Pleomorphic liposarcoma: 3
   11. Dedifferentiated liposarcoma: 3
   12. Pleomorphic rhabdomyosarcoma: 3
   13. Poorly differentiated / pleomorphic leiomyosarcoma: 3
   14. Synovial sarcoma: 3
   15. Mesenchymal chondrosarcoma: 3
   16. Extraskeletal osteosarcoma: 3
   17. Extraskeletal Ewing sarcoma: 3
   18. Malignant rhabdoid tumour: 3
   19. Undifferentiated pleomorphic sarcoma: 3
   20. Undifferentiated sarcoma, NOS: 3
2. Mitotic count: This measures the number of mitotic figures (dividing cells) in the tumour, specifically in the most mitotically active area, by examining 10 successive high-power fields (HPFs) under a microscope.
   • 1 point: 0 – 9 mitoses
   • 2 points: 10 – 19 mitoses
   • 3 points: 20 or more mitoses
3. Tumour necrosis: Necrosis refers to the amount of dead tissue within the tumour. Tumours with more necrosis tend to be more aggressive. The scoring is based on the percentage of the tumour that is necrotic:
   • 0 points: No necrosis
   • 1 point: Less than 50% necrosis
   • 2 points: 50% or more necrosis

How is the final FNCLCC grade determined?

The final grade is determined by adding the scores for differentiation, mitotic count, and necrosis:

• Grade 1: Low-grade tumour, likely to grow slowly.
• Grade 2: Intermediate-grade tumour, may grow faster.
• Grade 3: High-grade tumour, more likely to grow quickly and spread.

Which soft tissue sarcomas are not graded according to the FNCLCC system?

Certain sarcomas are not graded using the FNCLCC system because they behave differently or have unique biological characteristics that do not fit the typical grading criteria. These sarcomas include embryonal and alveolar rhabdomyosarcoma, angiosarcoma, extraskeletal myxoid chondrosarcoma, alveolar soft part sarcoma, clear cell sarcoma, and epithelioid sarcoma. These types of tumours have distinct grading systems or criteria due to their specific patterns of growth and spread.

Can the FNCLCC grade be determined on a biopsy?

Yes, the FNCLCC grade can often be determined on a biopsy, a small tissue sample taken from the tumour. Pathologists examine the sample under a microscope and use the FNCLCC system to assign a grade. This pretreatment biopsy is especially important because it provides the baseline grade for the tumour, which can be used even after the tumour is removed surgically.

Can the FNCLCC grade be determined after treatment, such as radiation or chemotherapy?

After treatments like radiation or chemotherapy, the tumour can undergo changes that make it difficult to determine its grade accurately. These changes might include cell death, scarring, or alterations in the appearance of the remaining tumour cells. As a result, grading becomes unreliable after treatment. The grade determined on the pretreatment biopsy is typically used to assess the tumour even after it has been removed through surgery, as this reflects the tumour’s characteristics before treatment altered its appearance.