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Incidence

• Benign ST tumours are common – 3000 per 1,000,000 (precise data not available as large number of undiagnosed benign lumps in the population).
• Malignant ST tumours are rare – 30 per 1,000,000.
• Soft tissue sarcomas – 1% of all malignant tumours.
• Trying to differentiate benign and malignant soft tissue lumps:
• 99% of benign tumours are superficial.
• 95% of benign tumours are <5 cm.
• A third of sarcomas are superficial but with a median size of 5 cm.
• Two-thirds of sarcomas are deep, median diameter 9 cm (larger in UK than many other countries).
•  In clinical practice this means that:
• A mass that is small (less than 5 cm in its greatest dimension) is unlikely to be malignant, while a mass that is greater than 5 cm has at least a 20% chance of being a soft tissue sarcoma.¹
• Superficial lesions are more likely to be benign² and, when malignant, may have a better prognosis than deep lesions.³
• The thigh and buttocks are the two most common sites for soft tissue sarcomas. Any large deep mass in the thigh or buttocks should be considered at high risk for being a malignant lesion.

• Genetics – NF-1, Li-Fraumeni, retinoblastoma all increase the risk of soft tissue sarcoma.
• Chemical – dioxins may increase risk.
• Radiation – 50Gy
• Median 10 years after treatment, most commonly seen following radiotherapy for breast cancer (leading to angiosarcoma).

Diagnosis

• Features in history and examination:
• Painful
• Enlarging
• Recurrence (any tumour that recurs should be considered a sarcoma even if original histology reported as benign).
• Size >5 cm
• Deep to fascia
• These features were the basis for referral under 2-week wait suspected cancer referral. Any one feature is said to pose a 20% risk of malignancy and this is additive, i.e. a deep, painful lump has a 40% risk that it will be malignant.
• Updated NICE guidance for primary care now suggests referral for ultrasound for any unexplained lump.

• A common clinical error is to misdiagnose a haemorrhagic sarcoma as a haematoma. To prevent this mistake:
• Never accept this diagnosis unless:

1. Significant trauma.
2. Risk factors – i.e. warfarin, clopidogrel.
3. Beware the fictitious trauma history – ask specifically did the lump develop immediately after trauma.
4. Ensure correct magnetic resonance sequences done with contrast before accepting the diagnosis of a haematoma.
5. Lumps diagnosed as a haematoma must always be followed up clinically for resolution with a low threshold for repeat scanning, a haematoma should not enlarge.

Imaging

• Ultrasound can be used as a “screening” tool for superficial lesions. It can differentiate obviously benign lesions (ganglion/lipoma) from possible malignant lesions; however, it is operator dependent and is not diagnostic of malignancy.
• MRI with contrast is the gold standard. Many radiology departments do not routinely give contrast but this is required to exclude a soft tissue sarcoma. Contrast enhancement is a vital clue to whether a lesion is vascularised and therefore more likely to be malignant.
• If soft tissue sarcoma is a possible diagnosis following either ultrasound or MRI then the patient should be referred to a sarcoma diagnostic service.

Biopsy

• Should have MRI scan prior to biopsy as biopsy affects imaging appearances.
• Cases should be discussed at a sarcoma MDT prior to biopsy.
• Discussion between radiologist, pathologist and surgeon to decide which part of lesion to target by which method through which anatomical approach.
• Biopsy in line of definitive incision to allow excision.
• Violate minimum number of compartments.
• Not fine needle aspiration cytology. Cytology cannot diagnose sarcoma histological architecture – cells and stroma are required to diagnose sarcoma.
• Trucut core biopsy provides architecture allowing diagnosis.

Biopsy methods

• Large tumours are often biopsied under local anaesthesia (LA) in clinic without real time imaging guidance as it is possible to target tumour by referring to the MRI scan.
• Image guided – USS most commonly used but deeper lesions require CT guidance.
• Open/incisional – usually reserved if indeterminate results from image guided biopsy, requires meticulous haemostasis.
• Excisional – not routine practice, reserved for small lesions <2 cm or in the digits.

Treatment

• Surgery
• RXT
• Neo-adjuvant – before surgery
• Adjuvant – after surgery
• Chemotherapy
• Palliative
• Neo-adjuvant – uncommon in soft tissue sarcoma
• The initial aim in the treatment of soft tissue sarcoma is to remove the primary tumour and obtain local control (i.e. minimise the risk of local recurrence).
• For small tumours or low grade tumours it may be possible to achieve local control with surgery alone. Surgery requires excision of the tumour surrounded by a margin of normal tissue – i.e. the tumour cannot be “shelled” out of the plane of excision is through normal healthy tissue.
• Ideally tumours are excised with wide margins of 1–2 cm; however, the large size of tumours and proximity to vital neurovascular structures often limits margins to a few millimetres. Therefore to reduce the risk of local recurrence radiotherapy is required. The majority of soft tissue sarcomas require radiotherapy in addition to surgery because the tumour is either large, deep in location, has close surgical margins or a high grade (and often all of these risk factors). The local recurrence rate for surgery alone is approximately 10% which is reduced to 5% with the addition of radiotherapy.
• Radiotherapy traditionally is administered approximately 6 weeks after surgery (60 Gy in 30 fractions). However, there is a risk of stiffness, lymphoedema and fracture with these doses of radiotherapy. Therefore, there has been a shift towards preoperative radiotherpapy (50 Gy in 25 fractions). The lower dose may reduce the long term consequences of radiotherapy but offer equivalent local control rates.
• Chemotherapy is currently not effective in the treatment of most soft tissue sarcomas. There may be some effect in some histiotypes but largely it is reserved for use in a palliative context to try and increase survival once pulmonary metastasis have developed.

Prognosis and outcome

• Survival:

1. 50–60% 5 years
2. Size, stage, grade are predictors of prognosis – see staging above.

• Local recurrence – the development of local recurrence appears to lead to a worse outcome.
• Metastases – once metastases develop most patients are non-curative and median survival is 12 months from the development of pulmonary metastases. Occasionally resection of a solitary metastasis after a significant disease-free interval may enhance survival.

• Specific tumour details are not extensively discussed in the FRCS vivas but do feature in the MCQ. A working knowledge of the following tumours will aid clinical practice.

Benign lipomas

• Benign tumour composed of mature white adipocytes.
• Subcutaneous, intramuscular or intermuscular tumours of mature fat.
• Most are not painful (angilipomas are the exception, small superficial painful lesions).
• Plain X-rays may show a radioluscent region in the soft tissues.
• MRI shows a well demarcated lesion with exactly the same signal as fat.
• If no symptoms and definite radiological diagnosis, leave alone.
• If mass growing or causing symptoms excise with a marginal line of resection, i.e. shell out.
• Recurrence uncommon.
• Subgroups are spindle cell, cell lipoma, and pleomorphic lipoma are benign despite the use of the terms spindle and pleomorphic!

Malignant lipomatous tumours

Liposarcoma

• Malignant tumours with differentiation towards fatty tissue.
• Heterogenous group of tumours with the presence of signet ring type cells(lipoblasts) in common.
• Subtypes of liposarcoma incude: lipoma like, sclerosing, inflammatory, dedifferentiated, myxoid, round cell, pleomorphic.
• Range from low grade to high grade.
• Low grade liposarcomas – can be difficult to differentiate between a benign lipoma and a low grade liposarcoma.
• Atypical lipomatous tumour is the name given to well differentiated lipoma liposarcoma of the extremities. These are often very large tumours (mean 18 cm). Higher rate of local recurrence than with lipomas but with minimal propensity for metastatic disease.
• Low grade liposarcoma usually treated with surgical excision alone.
• High grade liposarcomas treated with wide local excision and radiotherapy.

Benign peripheral nerve tumours

Neurilemmoma (benign schwannoma)

• Benign nerve sheath tumour.
• Young to middle aged patients.
• Usually asymptomatic apart from the mass.
• MRI scan shows eccentric mass arising from a peripheral nerve.
• Histologically contains Antoni A or Antoni B cells.
• Antoni A – compact spindle cells, twisted nuclei, indistinct cytoplasm, clear vacuoles.
• Antoni B – less cellular.
• Treat by shelling our from the nerve leaving the nerve intact.

Neurofibroma

• Solitary or multiple (see neurofibromatosis).
• Most are superficial, grow slowly and are painless.
• When they involve a major nerve they can expand the nerve in a fusiform fashion.
• Histologically, interlacing bundles of elongated cells with wavy dark staining nuclei.
• Treatment – usually leave alone but if symptomatic excision with a marginal margin.
• In neurofibromatosis, malignant change occurs in 5–30% of patients.

Malignant nerve tumours

• Malignant peripheral nerve sheath tumours account for 5–10% of soft tissue sarcomas. They can occur in the normal population but have a higher incidence in patients with NF-1.##

Benign vascular tumours

Haemangioma/arteriovenous malformations

• Seen in children and adults.
• Intramuscular angiomas are a proliferation of benign vascular channels within skeletal muscle, mainly veins but also other vessels.
• Venous haemangiomas are composed exclusively of thick veins.
• Arteriovenous malformations/haemangiomas are benign vascular lesions characterised by the presence of arteriovenous shunts. These do not usually spontaneously regress unlike juvenile cutaneous haemangiomas.
• Haemangiomas
• If large, patients complain due to symptoms of venous engorgement (aching).
• Plain X-ray can show small pleboliths.
• MRI scan shows a heterogenous lesion with many small blood vessels.
• Treat non-operatively as very high recurrence rate (30–50%). Embolisation or sclerotherapy may improve symptoms.

Malignant vascular tumours

Angiosarcoma

• Rare
• Associated with previous radiotherapy or chronic lymphoedema (Stewart–Treves syndrome).
• Tumour resembles the endothelium of blood vessels.
• Treatment depends on grade and location of lesion. Generally associated with a poor prognosis (50% one year survival).

Ganglia (see hand tumours)

• Synovial proliferative disorders.

Pigmented villonodular synovitis

• This is a true neoplasm.
• Exuberant proliferation of synovial villi and nodules.
• Most common in the knee, followed by hip and shoulder.
• Symptoms include painful swollen joint.
• Aspiration reveals a bloody effusion.
• X-ray may show cystic.
• Histologically, highly vascular villi lined with plump hyperplastic synovial cells, haemosiderin stained multinucleated giant cells and chronic inflammatory cells.
• Often requires MDT discussion as appearances can be mimicked by haemarthrosis of the joint unless radiologists and pathologists discuss the case.
• Associated with high rates of recurrence, likely to reflect non-specialised tumour surgeons underestimating the magnitude of surgery required (20–40%).
• Often require complete synovectomy to eliminate disease.

Giant cell tumour of the tendon sheath (see hand tumours)

• Second most common hand mass (ganglia more common) and is the most common neoplasm in the hand.
• Benign but recurrent lesion originating in the tendon sheaths or joint synovium.
• Usually seen on the palmar surface of the digits especially the PIP joint of the index and middle fingers.
• Recurrence rate of 30% in the literature but with meticulous surgery recurrence rates very low.

Synovial chondromatosis

• Typically affects adults aged 30–50 years.
• Present with pain, stiffness and swelling.
• X-rays show fine stippled calcification.
• Histologically varies between metaplasia of synovial tissue to firm nodules of hyaline cartilage.
• Treat with synovectomy and removal of loose bodies.

Superficial fibromatosis (see hand section)

• Fibroblastic proliferations arising in palmer fascia (Dupytren’s disease) planter fascia (Ledderhose disease), penile fascia (Peyronie’s disease) and soft tissues on dorsum of interphalangeal joints (Garrod’s pads).

Extra-abdominal Desmoid tumour – fibromatosis

• Most locally invasive of the benign soft tissue tumours.
• Most common in adolescents and young adults.
• Rock hard on palpation.
• Histologically well differentiated fibroblasts and abundant collagen.
• Infiltrates surrounding tissues.
• Local recurrence common so surgery is usually avoided.
• Due to high recurrence rate should be managed by a sarcoma team.
• Treatment usually medical with estrogen manipulation, e.g. tamoxifen.
• Radiotherapy and chemotherapy used in aggressive cases.

Rhabdomyosarcoma

• The most common sarcoma in young patients – 3.5% of malignancy in 0–14 year olds.
• Highly malignant.
• Grows rapidly.
• Spindle cells in parallel bundles, multinucleated giant cells and racquet shaped cells, cross-striations within the tumour cells (rhabdomyoblasts).
• Sensitive to multi-agent chemotherapy.
• Treat with preoperative chemotherapy, followed by wide surgical excision and radiotherapy.
• 70% 5-year survival for non-metastatic patients.

Synovial sarcoma

• Highly malignant.
• Occurs in close proximity to joints but rarely from an intra-articular lesion.
• Often have significant pain.
• Does not arise from synovium. Cell of origin unknown.
• X-rays may show mineraalisation within the lesion.
• Histologically, tumour is biphasic with a spindle cell component and an epithelial component.
• Has a specific chromosomal translocation t(X;18)(p11;q11) that leads to the formation of a SS18-SSX fusion gene (SS18 also known as SYT or SSXT which causes confusion and any of these can appear in exam questions!).
• Treat with wide excision and adjuvant radiotherapy.

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