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Adult Soft Tissue Sarcoma Treatment (PDQ®)

Cellular Classification of Adult Soft Tissue Sarcoma

Soft tissue sarcomas are classified histologically according to the soft tissue cell of origin. Additional studies, including electron microscopy, specialized immunohistochemistry, flow cytometry, cytogenetics, and tissue culture studies may allow identification of particular subtypes within the major histologic categories. For example, S100 antigen suggests neural sheath origin, cytokeratin suggests epithelioid or synovial cell origin, and factor VIII-related antigen suggests endothelial origin. Likewise, some subtypes of sarcomas have characteristic genetic markers, but these markers are not generally used in the routine clinical setting (e.g., t(X;18)(p11;q11) in synovial sarcomas and t(12;16)(q13;p11) in myxoid and round-cell sarcomas).[1-3]

The histologic grade reflects the metastatic potential of these tumors more accurately than the classic cellular classification listed below. Pathologists assign a grade based on the number of mitoses per high-powered field, the presence of necrosis, cellular and nuclear morphology, and the degree of cellularity; discordance among expert pathologists regarding tumor grade, and even histologic subtype, can be substantial.[4]

The World Health Organization lists the following cell types in its classification of soft tissue sarcomas:[5,6]

  • Adipocytic tumors.
    • Dedifferentiated liposarcoma.*
    • Myxoid/round cell liposarcoma.
    • Pleomorphic liposarcoma.
  • Fibroblastic/myofibroblastic tumors.
    • Fibrosarcoma.**
    • Myxofibrosarcoma, low grade.
    • Low-grade fibromyxoid sarcoma.
    • Sclerosing epithelioid fibrosarcoma.
  • So-called fibrohistiocytic tumors.
    • Undifferentiated pleomorphic sarcoma/malignant fibrous histiocytoma (MFH) (including pleomorphic, giant cell, myxoid/high-grade myxofibrosarcoma, and inflammatory forms).
  • Smooth muscle tumors.
    • Leiomyosarcoma.
  • Skeletal muscle tumors.
    • Rhabdomyosarcoma (embryonal, alveolar, and pleomorphic forms).
  • Vascular tumors.
    • Epithelioid hemangioendothelioma.
    • Angiosarcoma, deep.***
  • Tumors of peripheral nerves.
    • Malignant peripheral nerve sheath tumor.
  • Chondro-osseous tumors.
    • Extraskeletal chondrosarcoma (mesenchymal and other variants).
    • Extraskeletal osteosarcoma.
  • Tumors of uncertain differentiation.
    • Synovial sarcoma.
    • Epithelioid sarcoma.
    • Alveolar soft part sarcoma.
    • Clear cell sarcoma of soft tissue.
    • Extraskeletal myxoid chondrosarcoma.
    • Primitive neuroectodermal tumor (PNET)/extraskeletal Ewing tumor.
    • Desmoplastic small round cell tumor.
    • Extrarenal rhabdoid tumor.
    • Undifferentiated sarcoma; sarcoma, not otherwise specified (NOS).

[Note: *It is recognized that dedifferentiated liposarcoma primarily arises in the context of deep atypical lipomatous tumor/well-differentiated liposarcoma, a sarcoma of intermediate malignancy because of the lack of metastatic capacity. **The category of fibrosarcoma can be inclusive of fibrosarcomatous differentiation in dermatofibrosarcoma protuberans. ***Cutaneous angiosarcoma may be difficult to stage using the AJCC system. (Refer to the PDQ summary on Gastrointestinal stromal tumor [GIST] summary for more information.]

References

  1. Singer S, Nielsen T, Antonescu CR: Molecular biology of soft tissue sarcoma. In: DeVita VT Jr, Lawrence TS, Rosenberg SA: Cancer: Principles and Practice of Oncology. 9th ed. Philadelphia, Pa: Lippincott Williams & Wilkins, 2011, pp 1522-32.
  2. Singer S, Maki RG, O'Sullivan B: Soft tissue sarcoma. In: DeVita VT Jr, Lawrence TS, Rosenberg SA: Cancer: Principles and Practice of Oncology. 9th ed. Philadelphia, Pa: Lippincott Williams & Wilkins, 2011, pp 1533-77.
  3. Malawer MM, Helman LJ, O'Sullivan B: Sarcomas of bone. In: DeVita VT Jr, Lawrence TS, Rosenberg SA: Cancer: Principles and Practice of Oncology. 9th ed. Philadelphia, Pa: Lippincott Williams & Wilkins, 2011, pp 1578-1609.
  4. Alvegård TA, Berg NO: Histopathology peer review of high-grade soft tissue sarcoma: the Scandinavian Sarcoma Group experience. J Clin Oncol 7 (12): 1845-51, 1989. [PUBMED Abstract]
  5. Soft tissue sarcoma. In: Edge SB, Byrd DR, Compton CC, et al., eds.: AJCC Cancer Staging Manual. 7th ed. New York, NY: Springer, 2010, pp 291-6.
  6. Brodowicz T, Schwameis E, Widder J, et al.: Intensified Adjuvant IFADIC Chemotherapy for Adult Soft Tissue Sarcoma: A Prospective Randomized Feasibility Trial. Sarcoma 4 (4): 151-60, 2000. [PUBMED Abstract]
  • Updated: February 28, 2014