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Staging and Grading Systems for Childhood Soft Tissue Sarcoma

    Table 6. Anatomic Stage/Prognostic Groupsa continued...

    Grade III

    Grade III lesions are similar to Grade II lesions and include certain tumors known to be clinically aggressive by virtue of histologic diagnosis and non-Grade I tumors (with >4 mitoses per 10 high-power fields or >15% necrosis):

    • Pleomorphic or round-cell liposarcoma.
    • Mesenchymal chondrosarcoma.
    • Extraskeletal osteogenic sarcoma.
    • Malignant triton tumor.
    • Alveolar soft part sarcoma.
    • Any other sarcoma not in grade I with >15% necrosis and/or ≤5 mitotic figures per 10 high-power fields (40X objective).

    Any other sarcoma not included in grade I in which more than 15% of the surface area is necrotic or in which there are more than four mitotic figures per ten high-power fields (40X objective) is considered a grade III lesion. Marked atypia and cellularity are less predictive but may assist in placing tumors in this category.

    FNCLCC grading system

    The FNCLCC histologic grading system was developed for adults with STS. The purpose of the grading system is to predict which patients will develop metastasis and subsequently benefit from adjuvant chemotherapy.[8,9] The system is described in Tables 7 and 8.

    Table 7. FNCLCC Histologic Grading System

    FNCLCC = Fédération Nationale des Centres de Lutte Contre Le Cancer; HPF = high-power field.
    Tumor Differentiation 
    Score 1Sarcoma closely resembling normal adult mesenchymal tissue (e.g., well-differentiated liposarcoma)
    Score 2Sarcomas for which histologic typing is certain (e.g., myxoid liposarcoma)
    Score 3Embryonal and undifferentiated sarcomas, sarcomas of doubtful type, and synovial sarcomas
     
    Mitotic Count 
    Score 10–9 mitoses per 10 HPF
    Score 210–19 mitoses per 10 HPF
    Score 3≥20 mitoses per 10 HPF
     
    Tumor Necrosis 
    Score 0No necrosis
    Score 1<50% tumor necrosis
    Score 2≥50% tumor necrosis

    Table 8. Histologic Grade Determined by Total Score

    Total ScoreHistologic Grade
    2–3Grade I
    4–5Grade II
    6–8Grade III

    Prognostic Significance of Tumor Grading

    The two grading systems described above have proven to be of prognostic value in pediatric and adult nonrhabdomyosarcomatous STSs.[10,11,12,13,14] In a study of 130 tumors from children and adolescents with nonrhabdomyosarcomatous STS enrolled in three prospective clinical trials, a correlation was found between the POG-assigned grade and the FNCLCC-assigned grade. However, grading did not correlate in all cases; 44 tumors received discrepant grades and their clinical outcome was intermediate between those who were assigned grades 1 and 2 or 3 in both systems. A mitotic index of 10 or greater emerged as an important prognostic factor.[15] The recently completed COG-ARST0332 trial will analyze data comparing the POG and FNCLCC pathologic grading systems to determine which system better correlates with clinical outcomes.

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