Soft tissue tumours are classified using the WHO classification, based on the morphological appearances of the tumour and whether or not it is benign or malignant. There are more than 50 variants of soft tissue sarcoma. The classification includes:

• adipocytic tumours (eg lipoma, liposarcoma)
• fibroblastic/myofibroblastic tumours (eg elastofibroma, adult fibrosarcoma)
• so-called fibrohistiocytic tumours (eg GCT of tendon sheath, pleomorphic MFH)
• smooth muscle tumours (eg angioleiomyoma, leiomyosarcoma)
• pericytic tumours (eg glomus tumour)
• skeletal muscle tumours (eg rahbdomyoma, rhabdomyosarcoma)
• vascular tumours (eg haemangioma, angiosarcoma)
• chondro-osseous tumours (eg soft tissue chondroma, extraskeletal osteosarcoma)
• tumours of uncertain differentiation (eg intramuscular myxoma, synovial sarcoma)