Malignant Soft Tissue Tumours
General Points
- All malignant soft tissue tumours are called sarcomas.
- They are sub-classified by tissue of origin (e.g., liposarcoma, fibrosarcoma).
- They tend to be >5 cm in size at presentation but may be smaller.
- Sarcomas have a centripetal growth pattern.
Epidemiology
- Tend to be in older patients (80% >50 years).
- Males > Females.
- They are fairly rare.
Worrying Clinical Features
- Fast growing.
- Painful.
- Large size (>5 cm).
- Neurologic, vascular symptoms.
- Tethering to other structures.
Imaging
- MRI scan of most sarcomas is indeterminate, i.e., they do not look like a lipoma, ganglion, or other characteristic benign soft tissue lesion.
Biopsy
- Usually require an incisional or needle biopsy.
- Never do an excisional biopsy without being sure of what the lesion is.
Adjuvant Therapy
- Chemotherapy is not of use in soft tissue sarcomas (except Ewings & Rhabdo).
- Radiation therapy is useful (external beam or brachytherapy).
- No overall difference in pre- or post-operative radiotherapy.
Pre-operative Radiotherapy
- Leaves a thick fibrous capsule around the tumour, which is easier to excise.
- Smaller dose required.
- Less radiation-induced sarcoma; skin/joint contracture.
- More wound complications and higher infection risk.
- Wait 3 weeks after radiotherapy before operating.
Post-operative Radiotherapy
- Fewer wound problems once wounds have healed.
- Higher dosage required = more other complications.
Surgical Principles
- Use a tourniquet without exsanguination.
- Meticulous haemostasis.
- Drain through or directly in line with the wound.
- Excise the biopsy track.
- Performed by or in conjunction with a tumour unit.
- Safe margins generally need free flap reconstruction.
- Wide excision is recommended.
- Marginal excision would go through the reactive zone.
- Decision to salvage or amputate is the same as for bone tumours – can a functional, disease-free limb be left?
Outcomes
- Dependent on tumour grade.
- 50% with high-grade sarcoma die from the disease.
- Poor prognostic factors:
- High grade.
- Metastases at presentation (lymph node, lungs).
- Depth of tumour.
- Size of tumour.
- Vascular compromise of the limb.
Subtypes
- Synovial Sarcoma
- Clear Cell Sarcoma
- Epithelioid Sarcoma
- Malignant Fibrous Histiocytoma (MFH)
- Liposarcoma
- Fibrosarcoma
- Rhabdomyosarcoma
- Leiomyosarcoma
- Neurofibrosarcoma (Malignant Nerve Sheath Tumour)
Synovial Sarcoma
Epidemiology - Most common soft tissue sarcoma in young adults (14–40 years).
Aetiology - Abnormality of SYT gene. - Translocation of X18 chromosome.
Clinical Features - Highly malignant, high-grade lesion. - Most common soft tissue sarcoma in the foot.
Location - Para-articular regions, especially the knee; rarely involves a joint.
Imaging - Low signal T1, high signal T2. - Calcifications within the lesion.
Pathology - High grade. - Biphasic histology – combination of fibrous (spindle cell) and epithelial cells.
Management - Consider chemotherapy as adjunct to surgery – young patients tolerate better.
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Clear Cell Sarcoma
Epidemiology
- Young adults (20–40 years)
- Females > Males (one of the few MSK tumours)
Aetiology
- Translocation of chromosomes 12 and 22
Clinical Features
- Most common soft tissue sarcoma of the foot
- Associated with tendon sheaths and aponeuroses
- Highly malignant with poor prognosis if pulmonary metastases
- Produces melanin – malignant melanoma of soft parts
Imaging
- 2–6 cm
- Low signal T1, high signal T2
- Indeterminate on MRI – needs biopsy
Pathology
- Intracellular melanin
- Nests of round cells with clear cytoplasm
Epithelioid Sarcoma
Epidemiology
- Young adults
Aetiology
- Unknown
Clinical Features
- Most common sarcoma in the hand
- Closely related to tendon sheaths
- Easily mistaken for something else and resected – high local recurrence
- Slow-growing and pain-free, therefore may seem benign
Imaging
- Calcifications
- MRI – low signal on T1, high signal on T2
- Indeterminate – needs biopsy
Management/Outcomes
- Wide excision and radiotherapy
- Often amputation needed
- Late metastases to lung are common
- Prognosis is poor
Malignant Fibrous Histiocytoma (MFH)
Epidemiology
- Most common sarcoma of older adults (>55 years)
Clinical Features
- Slow-growing painless mass
- Can become very big
- May cause systemic symptoms like fever and weight loss
Imaging
- Low signal T1, high signal T2
- Indeterminate – needs biopsy
Pathology
- Haphazard, pleomorphic histiocytic cells
Outcomes
- 50% survival at 5 years
Liposarcoma
Epidemiology
- Second most common soft tissue sarcoma
- Older adults (>50 years)
Clinical Features
- Almost never in subcutaneous tissue, usually deep
- Mesenchymal origin – unrelated to lipomas
- Can get very large
- Often painless, slow-growing mass but may suddenly accelerate growth
- May be low, intermediate, or high grade
Pathology
- Signet cells (typical type of lipoblast)
Imaging
- MRI indeterminate
Management & Outcomes
- Low grade: Marginal excision with no adjuvant therapy
- High grade: Wide excision and adjuvant chemo/radiotherapy
- Metastases more likely with higher grades
Fibrosarcoma
Epidemiology
- Middle-aged adults
- Rare
Clinical Features
- Slow-growing
- Around the knee
- Painless
Imaging
- Indeterminate – needs biopsy
Pathology
- Spindle cells
Management/Outcome
- Wide excision and adjuvant radiotherapy
- Metastasizes in 50%
Rhabdomyosarcoma
Epidemiology
- Most common soft tissue tumour of children
Clinical Features
- Skeletal muscle tumour
- Fast-growing, painless mass
- Only 15% in the extremities – usually in the thigh/forearm
Imaging
- Indeterminate – needs biopsy
Pathology
- Positive immunohistochemistry for Myoglobin, Desmin, and MyoD1
Management
- Chemotherapy is the adjuvant therapy of choice
- Radiotherapy for incomplete margins
Outcomes
- 70% survival in children
- Worse prognosis in adults
Leiomyosarcoma
- Smooth muscle tumour
- Similar characteristics to rhabdomyosarcoma
- Often involves blood vessels
Neurofibrosarcoma (Peripheral Nerve Sheath Tumour)
Epidemiology
- Middle-aged adults
Aetiology
- De Novo: Rare
- Secondary to Neurofibromatosis type 1 (50%)
Clinical Features
- Affects deep, large nerves (e.g., sciatic, sacral, or brachial plexus)
- Pain more common in NF1
Imaging
- Indeterminate on MRI
- Appears fusiform, eccentrically placed within a major nerve
Pathology
- S100 staining positive
- Spindle cells in a wavy pattern
Management
- Wide excision with radiotherapy
- Better survival for solitary lesions than those secondary to NF1
Angiosarcoma
- Highly malignant
- Rare
- Often requires amputation due to vascular involvement
- Poor prognosis