Overview
Sarcomas are cancers that develop from the body’s supporting tissues - the mesenchymal cells - unlike carcinomas that develop from epithelial cells, such as the skin or the cells lining the intestines, lungs and glands. Sarcomas are very rare tumours that are found in the muscles, fat, nerves, blood vessels, cartilage and bones.
Sarcomas are often not diagnosed at first presentation. As a general rule, any swelling in the soft tissues greater than 5 cm in size could be a sarcoma and should be referred to a specialist centre for investigation.
Cells in sarcomas often look like cells from cartilage, fat or muscle. This is relevant when deciding on the most appropriate treatment.
The treatment for different types of sarcoma varies according to the type of tumour growth rate and other factors.
Sarcomas often affect younger people. There tend to be two age peaks:
- childhood and adolescents
- those over 55 years old
Many sarcomas can be cured if diagnosed early and treated correctly.
The lower limbs are the most common site of origin for soft tissue sarcomas in adults. In decreasing order of frequency of sarcoma development, the lower limbs are followed by the upper limbs, the torso and then the head and neck region.
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Key Figures
Overall, sarcomas account for just 1% of all cancers. However, in children sarcomas account for 8% of all cancers.
Rhabdomyosarcoma is the most common soft tissue sarcoma among children aged 0-14 years old, representing nearly 50% of soft tissue sarcomas for this age range (SEER Statistics).
Sarcomas are slightly more common in males.
The incidence of the various forms of sarcoma varies enormously according to the tumour type.
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Cancer Types
Cells in sarcomas often look like cells from cartilage, fat, muscle or some other specific tissues and what they look like is relevant when deciding on the most appropriate treatment. In the sections below, tumours are categorised according to the tissues that they resemble.
Muscle Cell Sarcomas
Muscle cell sarcomas are very rare. There are two main types:
- Rhabdomyosarcomas which resemble cells from striated muscles. Although they are very rare, they still account for 50% of all soft tissue sarcomas in childhood.
- Leiomyosarcomas which resemble cells from the smooth muscles found in the stomach or heart.
Bone Cell Sarcomas
Most cancers found in bones are not sarcomas but lung, breast and prostate cancers that have spread to the bones causing secondary cancers. True bone cell sarcomas include:
Osteosarcoma
Osteosarcomas affect mainly the young and the very old. In children, teenagers and young adults the most likely symptoms are an unusual pain or bony lump. In elderly people, sarcomas can develop from Paget's disease and are often noticed following a fall. Paget's disease of the bone affects people over the age of 40, more often men than women, and occurs most commonly in the UK.
Chondrosarcoma
Chondrosarcoma is a type of sarcoma whose cells resemble cartilage tissue cells. They are found in the thigh, arm, pelvis, knee, spine and ribs.
Ewing's Sarcoma
Ewing's sarcoma is the name given to a very rare group of sarcomas affecting teenagers. Ewing’s sarcomas usually start in the bone – most commonly the pelvis, femur (thigh bone) and tibia (shin bone).
Gastrointestinal Stromal Tumours (GIST)
Gastrointestinal Stromal Tumours (GIST) are a rare sarcoma of the intestines (1-3% of all gastrointestinal malignancies) and are a form of sarcoma. 70% occur in the stomach and they can spread to the liver and elsewhere within the abdominal cavity.
Malignant Fibrous Histiocytoma (MFH)
Malignant Fibrous Histiocytoma (MFH) is an uncommon form of sarcoma found in the fibrous tissue around the bones.
Fatty Tissue Sarcomas
Liposarcomas have cells that resemble fat cells. There are three main types:
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Causes of Sarcomas
In most cases there is no clear reason for the sarcoma to have developed. The exceptions are:
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Prevention of Sarcomas
In most cases there is no clear reason for a sarcoma to have developed, so for most patients there are no risk factors to avoid.
Awareness is critically important in gaining early diagnosis. Any swelling in the soft tissues greater than 5cm in size could be a sarcoma and should be referred to a specialist centre for investigation. In practice, as many as 10% of all swellings of this size are sarcomas.
Patients with neurofibromatosis, Gardner syndrome and retinoblastoma should undergo regular check ups, so that any sarcomas that do develop can be diagnosed and treated early in the disease.
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Common Symptoms
The presence of a lump 5cm or more in diameter should always be treated with suspicion. Pain may be a feature in some sarcomas but more often lumps are painless and frequently attributed to a minor injury – in fact it is the minor injury which has drawn attention to a lump which has been growing in size over several months.
When sarcomas grow in the retroperitoneum (the inside back wall of the abdomen), they may not cause specific symptoms for some time. They may cause pain, intestinal obstruction or bleeding from the stomach or bowel or swelling due to their size in the abdomen. About 20% of sarcomas are retroperitoneal.
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Diagnostic Tests
A biopsy will confirm the diagnosis and the grade of tumour – both very important in determining the best options for treatment. Several types of biopsy may be used in diagnosing sarcomas. Doctors with experience in treating these tumours will choose one based on the size and location of the tumour. Most experts prefer a fine needle aspiration or a core needle biopsy as the first step.
Biopsies can be taken using:
- fine needle aspiration to obtain small fragments of tissue from the tumour mass
- core needle biopsy to obtain a larger, cylindrical piece of tissue
- excisional or incisional biopsy which is a small operation to cut out a piece of the tumour for examination
Good biopsy technique is essential and is one reason why tumours should be investigated in specialist centres. Poor technique can lead to tumour spread.
Imaging tests (including chest X-rays, ultrasound, CT, MRI and PET scans) are used to determine the exact size, position and shape of the tumour, and whether it has spread to other areas of the body. They are usually done once a diagnosis of sarcoma has been made.
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Treatment of Sarcomas
Successful treatment of sarcomas requires a specialist team of health professionals.
Surgery, radiotherapy, chemotherapy and, to a lesser extent, the newer targeted therapies (monoclonal antibodies) are all used to treat sarcomas. Usually more than one form of treatment is required.
Using the combined knowledge and skills of all the multidisciplinary team members, different treatments can be combined to produce better results than any one treatment given on its own.
The recommended treatment will depend on the type of tumour, its grade, where it is, whether it has spread to other areas and the patient’s own preferences once the options for treatment have been explained.
The aim of surgery is to remove the tumour or as much of the tumour as possible. Usually, the cancer is removed with a margin of normal tissue around it so that there is the maximum chance of removing all the malignant cells. This reduces the risk of the sarcoma coming back in the same place.
Local surgical treatment is planned to strike the right balance between removing the tumour and maintaining good function as far as possible.
Using radiotherapy, chemotherapy or both (chemoradiation) before surgery can in some cases reduce the size of the tumour and make surgery easier.
Radiotherapy can also be used as an alternative to surgery where this is not feasible.
In the past, sarcomas of the arms and legs were treated by amputation: however, it is now usually possible to remove just the cancer with a margin of tissue around it (particularly if further chemotherapy or radiotherapy is used).
Soft Tissue Sarcomas of the Arms and Legs
For small tumours (less than 5 cm) surgical excision with a wide margin may be the only treatment required. Larger tumours are treated with surgery and pre- or postoperative chemoradiation or chemotherapy depending on the tumour type.
Head and neck and abdominal tumours are treated using surgery to remove the entire tumour with a margin of normal tissue where possible. However, this can be very difficult so chemoradiation is often used as an alternative or in addition to surgery.
Stage IV: The usual treatment for stage IV sarcomas where the only spread is to lymph nodes is surgical removal of the primary (main) tumour with a wide margin of normal tissue whenever possible and surgical removal of nearby lymph nodes. This may be followed by radiation therapy. If the main tumour was large, the radiation therapy (with or without chemotherapy) may be given before surgery. Likewise, chemotherapy may be added to the postoperative radiation.
If a sarcoma has spread to distant areas of the body, a cure is often not possible. However, in some patients it may be beneficial to remove the main tumour and all of the metastases surgically but this is a contentious area.
For patients whose primary tumour and metastases cannot be completely removed by surgery, palliative radiotherapy and/or chemotherapy are recommended to relieve symptoms.
Sarcomas that recur can be treated with surgery, or radiotherapy. Chemotherapy is the usual treatment for distant metastases.
Osteosarcoma treatment depends on the exact type of osteosarcoma. Therapy is usually a combination of surgery (removing the tumour and replacing the bone with a bone graft or metal rod) and chemotherapy (usually ifosfamide, cisplatin, methotrexate, and doxorubicin). Radiotherapy is rarely used in treating osteosarcomas.
Ewing’s sarcomas are highly responsive to radiotherapy (unlike osteosarcomas) and so are treated with radiotherapy, as well as surgery and chemotherapy.
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Prognosis
The prognosis for any patient with a sarcoma will depend upon a number of factors including:
- site
- type
- size at diagnosis
- grade
- depth in the tissues
- presence of metastases
The smaller the tumour the better the prognosis is likely to be. Tumours under 5 cm in diameter are less likely have metastasised and so are more likely to be cured. Sarcomas nearer the surface are easier to treat and so have a better prognosis. High grade or undifferentiated sarcomas tend to metastasise earlier resulting in a poorer prognosis.
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Key Trends
Treatments for sarcoma are constantly developing.
Sarcomas are (and should be) treated in specialist units.
Use of the new targeted therapies (monoclonal antibodies) is an important aspect of research for many different types of sarcoma.
The quality of surgery is increasingly seen as essential to securing good results.
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