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Chapter 25: Soft Tissue Sarcomas

Elizabeth Montgomery

INTRODUCTION

Soft tissue sarcomas are a heterogeneous group. Because of their rarity, they frequently pose diagnostic problems for surgical pathologists. Accurate diagnosis of these tumors is enhanced by knowledge of the clinical features of the given lesions and, at times, by application of immunohistochemical and molecular techniques. In this chapter, the lesions are described essentially in accordance with the World Health Organization (WHO) classification.1 It is beyond the scope of this chapter to cover all described soft tissue entities; both expanded2 and concise3 textbooks are also available.

Grading and Staging

Grading soft tissue tumors applies only to sarcomas. Histologic grade is an important (if not the most important) prognostic parameter in soft tissue neoplasia.4 Therefore, general grading schemes have been devised and studied over the past several decades in that correlate with prognosis, recurrence, metastasis free, and overall survival4,5 but the French Federation of Cancer Centers system, that uses differentiation, mitosis, and necrosis in their grading system provides the best prognostic information6,7 (Table 25-1) and is the preferred one for the AJCC staging systems as of 2010.8

TABLE 25-1

French Federation of Cancer Centers (FNCLCC, Fédération Nationale des Centres de Lutte Contre le Cancer) Grading Systema

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TABLE 25-1

French Federation of Cancer Centers (FNCLCC, Fédération Nationale des Centres de Lutte Contre le Cancer) Grading Systema
Histologic Parameters

  • Tumor differentiation

  • Mitosis count

  • Tumor necrosis

Scores are added to assign grade

Grade

1: Score 2–3

2: Score 4–5

3: Score 6–8
Scoring Parameters
Score Differentiation Mitosis Necrosis
0 Not used Not used No necrosis
1 Resembling normal tissue 0–9/field <50% necrosis
2 Sarcomas for which histologic typing certain 10–19/field >50% necrosis
3 Embryonal and undifferentiated sarcomas >20/field
1B: Differentiation Scoresb
Histologic Type Tumor Differentiation Score
Well-differentiated liposarcoma 1
Myxoid liposarcoma 2
Round cell liposarcoma 3
Pleomorphic liposarcoma 3
Dedifferentiated liposarcoma 3
Conventional fibrosarcoma 2
Poorly differentiated fibrosarcoma 3
Well-differentiated malignant schwannoma 1
Conventional malignant schwannoma
Poorly differentiated malignant schwannoma 3
Epithelioid malignant schwannoma 3
Malignant triton tumor 3
Myxoid MFH 2
Storiform pleomorphic MFH 2
Giant cell and inflammatory MFH 3
Well-differentiated leiomyosarcoma 1
Conventional leiomyosarcoma 2
Poorly differentiated/pleomorphic/epithelioid leiomyosarcoma 3
Biphasic/monophasic synovial sarcoma 3
All rhabdomyosarcoma 3
Well-differentiated chondrosarcoma 1
Myxoid chondrosarcoma 2
Mesenchymal chondrosarcoma 3
Well-differentiated MPNST 2
Poorly differentiated MPNST 3

a Data from Guillou L, Coindre JM, Bonichon F, et al. Comparative study of the National Cancer Institute and French Federation of Cancer Centers Sarcoma Group grading systems in a population of 410 adult patients with soft tissue sarcoma, J Clin Oncol. January 1997;15(1):350–362.

b Modified with permission from Guillou L, Coindre JM, Bonichon F, et al. Comparative study of the National Cancer Institute and French Federation of Cancer Centers Sarcoma Group grading systems in a population of 410 adult patients with soft ...

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