Soft tissue tumours of the extremities

Soft tissue tumours are rare, and the exact proportion of benign to malignant lesions (sarcomas) is difficult to determine. A study of a hospital population found that benign lesions outnumbered malignant ones by 100:1; their incidence was about 300 per 100 000 population.¹ In an average general practice of 3000 patients, at least three cases of benign soft tissue tumour per year may be expected. However, only one case of soft tissue sarcoma would be expected in this population every 24 years.

More than 50 different types of soft tissue tumour are recognised, and management depends on the tumour stage, grade, and histological type. The consequences of a missed case of sarcoma are serious—even a low grade sarcoma may metastasise. In the experience of our unit, cases of soft tissue sarcoma are being referred with some delay. This may result in adverse consequences for patients and potential medicolegal implications. The National Institute for Health and Clinical Excellence (NICE) is currently producing outcome guidelines for bone and soft tissue sarcomas. In this editorial, we aim to raise the general index of suspicion concerning soft tissue sarcomas and thereby achieve earlier referral to specialist centres.

Symptoms of soft tissue sarcomas are often insidious. A discrete lump or diffuse swelling may be the only consistent presenting feature. Size is one of the most important clinical features of a soft tissue lesion. Any soft tissue lesion over 5 cm in maximum diameter has a 20% likelihood of being malignant.² Soft tissue malignancies are usually painless until the latter stages, when the tumour has encroached on adjacent structures either by direct invasion or by mass effect. This has previously been identified as a reason for delayed presentation of soft tissue sarcomas.³ Patients are much more likely to seek medical attention early if a swelling is associated with persistent pain.

The duration of symptoms combined with changes in symptoms is a useful diagnostic factor. A lesion that has been present for 20 years and has not changed in appearance is unlikely to be malignant. A recent increase in size, however, may represent sarcomatous transformation. A history of trauma can be elicited in many cases and is sometimes proffered as an explanation by the patient. This can be misleading because a trivial traumatic episode may be the reason why a patient notices his or her lump. Recent trauma should present with concurrent clinical evidence, such as bruising or abrasions. If the injury was some time in the past then why has the patient not recovered? An abscess or cellulitis has easily recognisable signs of inflammation, but a previously present mass or swelling may cloud the picture. A ganglion should transilluminate, and should raise suspicion if it does not. Small superficial lumps are more likely to be benign.

The commonest sites for soft tissue sarcomas of the extremities are the thigh and buttock, and lesions in these areas are more likely to be malignant than those in other locations.² A deep mass greater than 5 cm in diameter, located proximally in the limb in a patient older than 50, has a 50% chance of being malignant.² Other than a small peak in incidence in children, sarcomas are more common in elderly people. However, any tissue lesion under observation should give rise to suspicion, especially if it is enlarging. Patients with lumps should be reviewed again, preferably within six weeks of initial presentation. If a lump under observation has not resolved the diagnosis should be reconsidered and the patient referred.

Magnetic resonance imaging is the gold standard for investigation of soft tissue lesions and is mandatory in the investigation of large or poorly defined lesions. Obtaining such scans should not delay the referral of patients. We cannot stress too highly how important it is to voice concerns about possible malignancy at the time of requesting investigations. We advise direct discussion with a radiologist to arrange investigations, and if a delay occurs then the patient should be referred directly to a specialist centre. It is unacceptable that a patient with a possibility of a malignant lesion should have to wait months for “non-urgent” magnetic resonance imaging. Ultrasonography has been shown to be less reliable than magnetic resonance imaging for further investigation.³ Plain radiographs may be of value in showing the relation of the lesion to bone and its tissue density, as well as in identifying some lesions, such as of synovial sarcomas, of which up to 50% show calcification.

Any lesion causing concern, whether superficial or deep, should be referred to a specialist centre on an urgent “sarcoma two week wait” form, which will ensure the patient is seen within two weeks of the referral or be investigated with magnetic resonance imaging and possibly a tissue biopsy with a true cut needle. The message therefore is to be suspicious and have a low threshold for further investigation and referral. This will allow earlier detection and hopefully improve the prognosis of patients with soft tissue sarcomas.