The World Health Organisation (WHO) classification of soft tissue tumours is the most widely used pathology-based classification system for such disorders. The revision, part of the 5th edition of the WHO classification of soft tissue and bone tumours (volume 3), was published in 2020 and is reflected in the article below ¹.

Classification

Adipocytic tumours

• lipoma

• lipomatosis

• lipomatosis of nerve

• lipoblastoma and lipoblastomatosis

• angiolipoma

• myolipoma of soft tissue

• chondroid lipoma

• spindle cell/pleomorphic lipoma

• hibernoma

• atypical spindle cell/pleomorphic lipomatous tumour

• atypical lipomatous tumour/well-differentiated liposarcoma

• dedifferentiated liposarcoma

• myxoid liposarcoma

• pleomorphic liposarcoma

• myxoid pleomorphic liposarcoma

Fibroblastic/myofibroblastic tumours

• nodular fasciitis

• proliferative fasciitis and proliferative myositis

• myositis ossificans and fibro-osseous pseudotumour of digits

• ischaemic fasciitis

• elastofibroma

• fibrous hamartoma of infancy

• fibromatosis colli

• juvenile hyaline fibromatosis

• inclusion body fibromatosis

• fibroma of tendon sheath

• desmoplastic fibroblastoma

• myofibroblastoma

• calcifying aponeurotic fibroma

• EWSR1-SMAD3-positive fibroblastic tumour (emerging)

• angiomyofibroblastoma

• cellular angiofibroma

• angiofibroma of soft tissue

• acral fibromyxoma

• nuchal-type fibroma

• Gardner fibroma

• calcifying fibrous tumour

• palmar/plantar fibromatosis

• desmoid-type fibromatosis

• lipofibromatosis

• giant cell fibroblastoma

• dermatofibrosarcoma protuberans

• solitary fibrous tumour

• inflammatory myofibroblastic tumour

• low-grade myofibroblastic sarcoma

• superficial CD34-positive fibroblastic tumour

• myxoinflammatory fibroblastic sarcoma

• infantile fibrosarcoma

• adult fibrosarcoma

• myxofibrosarcoma

• low-grade fibromyxoid sarcoma

• sclerosing epithelioid fibrosarcoma

So-called fibrohistiocytic tumours

• tenosynovial giant cell tumour

• deep benign fibrous histiocytoma

• plexiform fibrohistiocytic tumour

• giant cell tumour of soft tissue

Vascular tumours

• haemangiomas

  • synovial haemangioma

  • intramuscular haemangioma

  • arteriovenous malformation/haemangioma

  • venous haemangioma

• anastomosing haemangioma

• epithelioid haemangioma

• lymphangioma and lymphangiomatosis

• tufted angioma and Kaposiform haemangioendothelioma

• retiform haemangioendothelioma

• papillary intralymphatic angioendothelioma

• composite haemangioendothelioma

• Kaposi sarcoma

• pseudomyogenic haemangioendothelioma

• epithelioid haemangioendothelioma

• angiosarcoma

Pericytic (perivascular) tumours

• glomangioma

• myopericytoma, including myofibroma

• angioleiomyoma

Smooth muscle tumours

• leiomyoma of deep soft tissue

• EBV-associated smooth muscle tumour

• inflammatory leiomyosarcoma

• leiomyosarcoma

Skeletal-muscle tumours

• rhabdomyoma

• embryonal rhabdomyosarcoma

• alveolar rhabdomyosarcoma

• pleomorphic rhabdomyosarcoma

• spindle cell/sclerosing rhabdomyosarcoma

• ectomesenchymoma

Gastrointestinal stromal tumours

• gastrointestinal stromal tumours

Chondro-osseous tumours

• soft-tissue chondroma

• extraskeletal osteosarcoma

Peripheral nerve sheath tumours

• schwannoma (including variants)

• neurofibroma (including variants)

• perineurioma

• granular cell tumour

• dermal nerve sheath myxoma

• solitary circumscribed neuroma

• ectopic meningioma and meningothelial hamartoma

• benign triton tumour/neuromuscular choristoma

• hybrid nerve sheath tumours

• malignant peripheral nerve sheath tumour

• malignant melanotic nerve sheath tumour

Tumours of uncertain differentiation

• intramuscular myxoma

• juxta-articular myxoma

• deep ("aggressive") angiomyxoma

• atypical fibroxanthoma

• angiomatoid fibrous histiocytoma

• ossifying fibromyxoid tumour

• myoepithelioma/myoepithelial carcinoma/mixed tumour

• pleomorphic hyalinizing angiectatic tumour of soft parts

• haemosiderotic fibrolipomatous tumour

• phosphaturic mesenchymal tumour

• NTRK-rearranged soft tissue neoplasms

• synovial sarcoma

• epithelioid sarcoma

• alveolar soft part sarcoma

• clear cell sarcoma of soft tissue

• extraskeletal myxoid chondrosarcoma

• desmoplastic small round cell tumour

• extrarenal rhabdoid tumour

• PEComa

• intimal sarcoma

• undifferentiated sarcoma

Changes from the prior version

Entities and variants

Entities include the following ^1-5:

• adipocytic tumours

  • atypical spindle cell/pleomorphic lipomatous tumour

  • myxoid pleomorphic liposarcoma

• fibroblastic and myofibroblastic tumours

  • angiofibroma of soft tissue

  • superficial CD34-positive fibroblastic tumour

  • EWSR-SMAD3-positive fibroblastic tumour

• vascular tumours

  • epithelioid haemangioendothelioma features two recognised subtypes

  • anastomosing haemangioma

  • tufted angioma and Kaposiform haemangioendothelioma are classified together

• pericytic (perivascular) tumours

  • myopericytoma, including myofibroma - subtype: cellular myofibroma/myopericytoma

• smooth muscle tumours

  • EBV-associated smooth muscle tumour

  • inflammatory leiomyosarcoma

• skeletal muscle tumours

  • spindle cell/sclerosing rhabdomyosarcoma - three subtypes

• tumours of uncertain differentiation

  • NTRK-rearranged soft tissue neoplasms

Other changes

• melanotic schwannoma: now renamed to malignant melanotic nerve sheath tumour

• dedifferentiated liposarcoma: adverse prognostic impact of myogenic and rhabdomyoblastic differentiation as well of a high grade on the FNCLCC (French Federation of Cancer Centres Sarcoma Group) grading system

• solitary fibrous tumour: 'extrapleural' has been removed