This article presents an overview of the different types and prevalence of soft tissue tumours, whether benign or malignant, and the tests involved in diagnosing them. This article explains the steps that anyone who has found a lump which may be large, painful and increasing in size should take.
- Incidence of soft tissue tumours
- Patterns of soft tissue tumours
- Causes of soft tissue tumours
- Symptoms of soft tissue tumours
- Investigations and diagnosis
Soft tissue tumours that appear as lumps and bumps are a diverse group of tumours that can be benign (non-cancerous) or malignant (cancerous). Soft tissue is defined as the supportive or connective tissue of the body and includes fibrous connective tissue, bone, muscle, fat, blood/lymph vessels and the nervous system. All lumps are usually referred to as tumours whether they are benign or malignant. Benign soft tissue tumours are relatively common in the general population. Benign tumours cannot spread to other parts of the body but they can continue to grow at the original site where they can cause a problem by pressing on the surrounding organs. They can also be cosmetically unsightly. Malignant soft tissue tumours are called sarcomas. They are a rare group of diverse tumours that grow in an uncontrollable manner and can invade adjacent tissue and spread (metastasise) around the body. There are also several conditions that can cause lumps and bumps that are not caused by tumours for example haematomas, cysts and inflammatory conditions.
The incidence of soft tissue tumours is difficult to determine since many are not reported. The majority of soft tissue lumps and bumps are benign. Benign soft tissue tumours out-number malignant tumours by a margin of approximately 100 to 1 with the most common being a fatty lipoma. Malignant soft tissue sarcomas are relatively uncommon tumours accounting for approximately 1% of all adult cancers. Estimates from the cancer networks in the United Kingdom suggest that about 3000 patients are diagnosed every year in the UK.
Soft tissue tumours can occur anywhere in the body. Malignant soft tissue sarcomas most commonly affect the lower limbs. Approximately 45% of sarcomas occur in the lower extremities, 15% between the membrane that lines the abdomen (the peritoneum) and the abdominal wall, 15% in the abdominal and chest wall, 15% in the upper extremities and 10% in the head-and-neck region. Soft tissue sarcomas may occur at any age, and although most common in middle aged and older adults, they are relatively more common in children and young adults, accounting for 7–10% of paediatric malignancies.
For the vast majority of soft tissue tumours the cause is unknown and they are believed to arise spontaneously. In a small proportion of patients there is a genetic link.
The clinical signs of a soft tissue tumour can vary. The most common is the presence of a painless, gradually enlarging lump. The size of soft tissue tumours at diagnosis varies according to where on the body they are located; tumours of the upper limbs and head or neck are usually smaller because they are likely to be noticed earlier, whereas tumours of the thigh and abdomen usually grow much larger before they are detected. In general, there are no completely reliable physical signs that can distinguish between a benign and a malignant lump. Any soft tissue lump showing any of the following four clinical signs should be considered to be malignant until proved otherwise:
- Increasing in size.
- Bigger than 5 cm.
- Deep in the body (i.e. not just under the skin).
During the investigation and treatment of benign soft tissue tumours, the potential of a lump being malignant needs to be kept in mind. The more of the clinical features listed above present, the greater the risk of malignancy, with increasing size being the best individual sign.
The identification of soft tissue sarcoma relies on a combination of clinical examination, imaging, and laboratory analysis. Anyone with a suspected soft tissue sarcoma should be referred to a diagnostic centre for a triple assessment consisting of clinical history and physical examination, appropriate imaging and a tissue biopsy (where a small sample will be taken to be examined under a microscope).
Clinical examination can be used to assess the tumour’s relationship to surrounding structures. A tissue biopsy is the definitive test to distinguish between benign and malignant tumours and can provide further helpful information (the specific type of sarcoma and grade of the tumour i.e. reflecting of how quickly the cancer may develop). Imaging demonstrates a tumour’s relation to important adjacent structures but cannot always reliably distinguish benign from malignant tumours.
The gold standard and only definitive test is a tissue biopsy. Core needle biopsy is simple, safe, and accurate and can be performed at the time of the initial consultation under local anaesthesia. The most important information required from the biopsy is whether the tumour is benign or malignant. The biopsy site should be placed in a position so that it is possible for the biopsy site and needle tract to be excised with the tumour at the definitive operation. This will ensure any contamination of normal tissue with cells from the tumour during the biopsy is removed. The biopsy should be performed either at a diagnostic clinic or by a sarcoma surgeon. Fine needle aspiration (FNA) is not recommended as a primary diagnostic method for soft tissue tumours.
Whilst the preferred method of imaging is magnetic resonance imaging (MRI), other options including computerised tomography (CT) or ultrasound (US) may be appropriate depending on local expertise and tumour type. Computed tomography of the thorax is preferable for detecting tumours that have spread from other sites (metastases). Positron emission tomography (PET) scanning, which produces a 3-D image, may be helpful in specific circumstances.
Soft tissue tumours are relatively common and are usually benign. However the possibility that a lump may be malignant should not be dismissed, particularly if it is increasing in size, larger than 5cm, deep in the body and/or is painful, and in these circumstances a formal diagnosis should be sought.