The World Health Organization lists the following cell types in its classification of soft tissue sarcomas:[1, 6, 7]
  1. Adipocytic tumors.
    1. Benign.
      • Lipoma.
      • Lipomatosis.
      • Lipomatosis of nerve.
      • Lipoblastoma/lipoblastomatosis.
      • Angiolipoma.
      • Myolipoma.
      • Chondroid lipoma.
      • Extra-renal angiomyolipoma.
      • Extra-adrenal myelolipoma.
      • Spindle cell/pleomorphic lipoma.
      • Hibernoma.
    2. Intermediate (locally aggressive).
      • Atypical lipomatous tumor/well-differentiated liposarcoma.
    3. Malignant.
      • Dedifferentiated liposarcoma.
      • Myxoid liposarcoma.
      • Pleomorphic liposarcoma.
      • Liposarcoma, not otherwise specified (NOS).
  2. Fibroblastic/myofibroblastic tumors.
    1. Benign.
      • Nodular fasciitis.
      • Proliferative fasciitis.
      • Proliferative myositis.
      • Myositis ossificans.
      • Fibro-osseous pseudotumor of digits.
      • Ischemic fasciitis.
      • Elastofibroma.
      • Fibrous hamartoma of infancy.
      • Fibromatosis colli.
      • Juvenile hyaline fibromatosis.
      • Inclusion body fibromatosis.
      • Fibroma of tendon sheath.
      • Desmoplastic fibroblastoma.
      • Mammary-type myofibroblastoma.
      • Calcifying aponeurotic fibroma.
      • Angiomyofibroblastoma.
      • Cellular angiofibroma.
      • Nuchal-type fibroma.
      • Gardner fibroma.
      • Calcifying fibrous tumor.
    2. Intermediate (locally aggressive).
      • Palmar/plantar fibromatosis.
      • Desmoid-type fibromatosis (previously called desmoid tumor or aggressive fibromatoses).
      • Lipofibromatosis.
      • Giant cell fibroblastoma.
    3. Intermediate (rarely metastasizing).
      • Dermatofibrosarcoma protuberans.
        • Fibrosarcomatous dermatofibrosarcoma protuberans.
        • Pigmented dermatofibrosarcoma protuberans.
      • Solitary fibrous tumor.
        • Solitary fibrous tumor, malignant.
      • Inflammatory myofibroblastic tumor.
      • Low-grade myofibroblastic sarcoma.
      • Myxoinflammatory fibroblastic sarcoma/atypical myxoinflammatory fibroblastic tumor.
      • Infantile fibrosarcoma.
    4. Malignant.
      • Adult fibrosarcoma.
      • Myxofibrosarcoma.
      • Low-grade fibromyxoid sarcoma.
      • Sclerosing epithelioid fibrosarcoma.
  3. So-called fibrohistiocytic tumors.
    1. Benign.
      • Tenosynovial giant cell tumor.
        • Localized type.
        • Diffuse type.
        • Malignant.
      • Deep benign fibrous histiocytoma.
    2. Intermediate (rarely metastasizing).
      • Plexiform fibrohistiocytic tumor.
      • Giant cell tumor of soft tissue.

      The malignant counterpart of so-called fibrohistiocytic tumors, formerly known as malignant fibrous histiocytoma and its subtypes was renamed undifferentiated sarcoma and was previously classified under the undifferentiated/unclassified sarcomas section.

  4. Smooth muscle tumors.
    1. Benign.
      • Deep leiomyoma.
    2. Malignant.
      • Leiomyosarcoma (excluding skin).

      Angioleiomyoma was reclassified under perivascular tumors.

  5. Pericytic (perivascular) tumors.
    • Glomus tumor (and variants).
      • Glomangiomatosis.
      • Malignant glomus tumor.
    • Myopericytoma.
      • Myofibroma (hemangiopericytoma are now included in recent WHO classification).
      • Myofibromatosis.
    • Angioleiomyoma.
  6. Skeletal muscle tumors.
    1. Benign.
      • Rhabdomyoma.
        • Adult type.
        • Fetal type.
        • Genital type.
    2. Malignant.
      • Rhabdomyosarcoma (embryonal [including botryoid, anaplastic], spindle cell/sclerosing, alveolar [including solid, anaplastic], and pleomorphic forms). (Refer to the PDQ summary on Childhood Rhabdomyosarcoma Treatment for more information.)
  7. Vascular tumors.
    1. Benign.
      • Hemangioma. (Refer to the PDQ summary on Childhood Vascular Tumors Treatment for more information.)
        • Synovial.
        • Venous.
        • Arteriovenous hemangioma/malformation.
        • Intramuscular.
      • Epithelioid hemangioma.
      • Angiomatosis.
      • Lymphangioma.
    2. Intermediate (locally aggressive).
      • Kaposiform hemangioendothelioma.
    3. Intermediate (rarely metastasizing).
      • Retiform hemangioendothelioma.
      • Papillary intralymphatic angioendothelioma.
      • Composite hemangioendothelioma.
      • Pseudomyogenic (epithelioid sarcoma-like) hemangioendothelioma.
      • Kaposi sarcoma.
    4. Malignant.
      • Epithelioid hemangioendothelioma.
      • Angiosarcoma of the soft tissue.
  8. Chondro-osseous tumors.
    • Soft tissue chondroma.
    • Extraskeletal mesenchymal chondrosarcoma.
    • Extraskeletal osteosarcoma.
  9. Gastrointestinal stromal tumors. (Refer to the PDQ summary on Gastrointestinal Stromal Tumors Treatment for more information.)
    1. Benign.
    2. Uncertain malignant potential.
    3. Malignant.
  10. Nerve sheath tumors.
    1. Benign.
      • Schwannoma (including variants).
      • Melanotic schwannoma.
      • Neurofibroma (including variants).
        • Plexiform neurofibroma.
      • Perineurioma.
        • Malignant perineurioma.
      • Granular cell tumor.
      • Dermal nerve sheath myxoma.
      • Solitary circumscribed neuroma.
      • Ectopic meningioma.
      • Nasal glial heterotopia.
      • Benign Triton tumor.
      • Hybrid nerve sheath tumors.
    2. Malignant.
      • Malignant peripheral nerve sheath tumor.
      • Epithelioid malignant peripheral nerve sheath tumor.
      • Malignant Triton tumor.
      • Malignant granular cell tumor.
      • Ectomesenchymoma.
  11. Tumors of uncertain differentiation.
    1. Benign.
      • Acral fibromyxoma.
      • Intramuscular myxoma (including cellular variant).
      • Juxta-articular myxoma.
      • Deep (aggressive) angiomyxoma.
      • Pleomorphic hyalinizing angiectatic tumor.
      • Ectopic hamartomatous thymoma.
    2. Intermediate (locally aggressive).
      • Hemosiderotic fibrolipomatous tumor.
    3. Intermediate (rarely metastasizing).
      • Atypical fibroxanthoma.
      • Angiomatoid fibrous histiocytoma.
      • Ossifying fibromyxoid tumor.
        • Ossifying fibromyxoid tumor, malignant.
      • Mixed tumor NOS.
      • Mixed tumor NOS, malignant.
      • Myoepithelioma.
      • Myoepithelial carcinoma.
      • Phosphaturic mesenchymal tumor, benign.
      • Phosphaturic mesenchymal tumor, malignant.
    4. Malignant.
      • Synovial sarcoma NOS.
        • Synovial sarcoma, spindle cell.
        • Synovial sarcoma, biphasic.
      • Epithelioid sarcoma.
      • Alveolar soft-part sarcoma.
      • Clear cell sarcoma of soft tissue.
      • Extraskeletal myxoid chondrosarcoma.
      • Extraskeletal Ewing sarcoma. (Refer to the PDQ summary on Ewing Sarcoma Treatment for more information.)
      • Desmoplastic small round cell tumor.
      • Extra-renal rhabdoid tumor.
      • Neoplasms with perivascular epithelioid cell differentiation (PEComa).
        • PEComa NOS, benign.
        • PEComa NOS, malignant.
      • Intimal sarcoma.
  12. Undifferentiated/unclassified sarcomas.
    • Undifferentiated spindle cell sarcoma.
    • Undifferentiated pleomorphic sarcoma.
    • Undifferentiated round cell sarcoma.
    • Undifferentiated epithelioid sarcoma.
    • Undifferentiated sarcoma NOS.