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Radiology of soft tissue sarcoma:discussion paperI

Stephen J Golding DMRD FRCR2Janet E Husband MRCP FRCRRoyal Marsden Hospital and Institute of Cancer Research, Sutton, Surrey

Soft tissue sarcomas form a large group of diverse forms of malignancy, the clinical behaviourof which is closely related to histology (Rosai 1976). Many carry a serious prognosis and it istherefore important that accurate diagnosis and assessment is made as quickly as possible. Awide range of imaging techniques is available, including ultrasound, nuclear medicine andcomputed tomography (CT) but, as sarcomas are seen infrequently, most hospitals areunlikely to have an established scheme of investigation. This paper is based on our experienceof more than 70 patients with soft tissue tumours seen at the Royal Marsden Hospital (Table1). We consider the relative merits of different imaging techniques in order to suggest ascheme for effective investigation, basing this on the clinical questions posed, namely: What isthe lesion? Where is it? Can it be resected? Are there distant metastases?

Table 1. Soft tissue sarcomas: diagnosis in 77 patients referred to theRoyal Marsden Hospital 1977-82

Fibrous histiocytoma 13Leiomyosarcoma 13Liposarcoma 9Fibrosarcoma 8Synovial sarcoma 8Undifferentiated sarcoma 7Rhabdomyosarcoma 6Epithelioid sarcoma 3Extraskeletal chondrosarcoma 2Neurofibrosarcoma 2Alveolar cell sarcoma 1Dermatofibrosarcoma 1Haemangiopericytoma 1Haemangiosarcoma ILeiomyoblastoma ILymphangiosarcoma I

What is the lesion?Plain radiography has a limited role in the diagnosis of soft tissue tumours because, althoughthe radiograph may show a soft tissue mass, the appearances are nonspecific (Figure IA).Frequently no mass can be identified by plain radiography, but in the limbs radiographs maybe valuable in the differential diagnosis if a palpable mass is due to an underlying primarybone neoplasm. In the abdomen plain radiography is unlikely to demonstrate soft tissuemasses and other investigations are usually necessary.Angiography may be helpful in confirming the presence of-a tumour in both the limbs and

abdomen since approximately two-thirds of sarcomas show tumour neovascularity.

'Based on paper read to Section of Oncology and Section of Radiology, 2 November 1981. Accepted 17 May 19822Present address: Churchill Hospital, Headington, Oxford

2 01982 The Royal Society of Medicine0 141-0768/82/090729-07/$O 1.00/0

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-B -Figure 1. Synovial sarcoma, left knee. A: Radiograph shows a soft tissue mass onthe medial aspect of the tibia (arrows). There is erosion of the underlying bone.B: The xeroradiograph provides a better demonstration of the soft tissue planesaround the tumour

Hypovascular tumours usually produce displacement of surrounding vessels. However, thereis no correlation between the degree of vascularity and the histology (Karp et al. 1980).

Examination of sarcomas with ultrasound may reveal a characteristic pattern (Karp et al.1980) in which the tumour has a relatively echo-free halo (Figure 2), but this appearance isalso seen in other lesions (D Cosgrove, personal communication) and cannot therefore beused to distinguish sarcomas from other masses.On computed tomography most soft tissue sarcomas appear as a mass with slightly lower

density than surrounding muscles (Golding & Husband 1982) (Figure 3). The appearances ofmost tumours are nonspecific (Egund et al. 1981) but well differentiated liposarcomas containlarge amounts of fat. This is readily appreciated at CT (Figure 4) so that a diagnosis of this

Figure 2. Retroperitoneal leimomyosac leiomyo- Figure 3. Malignant fibrous histiocytoma. CTsarcoma. Ultrasonogram of the left hypochon- scan' showing a well-defined tumour (T)drium showing the tumour (T) immediately inferior to within the gluteus muscle (M}. The tumour,the spleen (S). The centre of the tumour is echogenic but which is of slightly lower density thanthere is a relatively echo-free halo around the periphery. surrounding muscles, has spread throughoutNote the acoustic enhancement of the tissues beneath the the muscle compartment.tumour (arrows). (Reproduced by kind permission of DrDavid Cosgrove)

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L}' 'aFigure 4. Well-differentiated peritoneal liposarcoma. Figure 5. Rhabdomyosarcoma of right orbit. TheThe tumour, which occupies the right side of the axial CT image (above) shows the tumour (T)abdomen, is indistinguishable from normal fat but occupying the right orbit. A sagittalcontains areas of calcification and tissue of higher reconstruction (below) from. contiguous thindensity beneath the laparotomy scar (arrows). sections shows the e relationship of the tumour to(Reproduced from Husband & Fry 1981, by kind the superior and inferior walls of the orbit and thepermission) displacement of the optic globe (G)

tumour type can often be made (deSantos et al. 1981). Friedman et al. (1981) have shown thatthere is good correlation between tumour differentiation as represented by the amount of fatand the attenuation values at CT. The experimental work on tissue characterization ofsarcomas using dual energy CT has yet to be evaluated (Kan et al. 1980).Some sarcomas accumulate radionuclides (Levine et al. 1979, Zazzaro et al. 1980) but this is

a nonspecific effect. However, Chew & Hudson (1980) were able to distinguish lipomas andliposarcomas using isotope studies.At present, therefore, a specific diagnosis cannot be made on the radiological characteristics

of most sarcomas and imaging techniques have not replaced biopsy.

Where is the lesion?Accurate localization of tumours is required when planning surgery or radiotherapy. It isunusual for the tumour outline to be localized by plain radiography and although thedemonstration of soft tissue planes may be improved by xeroradiography (Figure iB), lessinformation is provided than by ultrasound or CT (Bernardino et al. 1981).

Ultrasound and CT may both define soft tissue tumours and their relations, both in theabdomen and in the limbs (Levine et al. 1979, Karp et al. 1980). Although CT appears to beinferior to ultrasound in domonstrating very small lesions in the limbs (Bernardino et at.1981), it generally provides more accurate localization (Heelan et al. 1979, Levine et al. 1979),additional useful information being obtained in up to 50%O of patients in some tumour types(deSantos et al. 1981). There are also some sites where CT is the imaging method of choice,notably the mediastinum and the head and neck (Figure 5).The margins of a hypervascular tumour may be evident on angiography but the relations of

the tumour are not usually shown and localization by angiography is generally inferior to thatprovided by CT, particularly if the tumour is hypovascular (Figures 6 and 7A, D).

Can it be resected?The most important reason for defining the relations of a tumour is to indicate whether anattempt at resection would be successful. Preferably the tumour should be removed with thesurrounding muscle compartment and fascial planes, the recurrence rate being closely relatedto the adequacy of surgery (Simon & Enneking 1976). Factors which preclude local resection

732 Journal of the Royal Society of Medicine Volume 75 September 1982

l- |_--_

Figure 6. Synovial sarcoma of left iliac fossa. A: Transfemoral aortogram showing spreading of the arteries in the iliacfossa around the tumour, which contains areas of calcification (arrows). B: CT scan shows limits of the mass whichoccupies the iliac fossa (arrows) and has involved both the psoas and iliacus muscles. (P= right psoas muscle, 1= rightiliacus muscle)

are extension through compartment boundaries, erosion of underlying bone and involvementof adjacent vessels (Shiu et al. 1975).

Involvement of bone may be evident on plain radiographs (Figure 1) and may also bedemonstrated by CT or skeletal scintigraphy. However, the presence of increased nuclideuptake in the bone adjacent to a tumour does not necessarily indicate infiltration (Simon &Enneking 1976).

Involvement of local vessels may be shown by angiography and ultrasound (Figure 7B, C),but when CT is used to assess the tumour the vessels may conveniently be examined by givingintravenous contrast medium during the examination. Direct tumour invasion of local veinscan also be demonstrated by contrast medium infusion into a peripheral vein distal to thetumour during scanning (Figure 7E) (Egund et al. 1981). This technique is probably morereliable than ultrasound (Bernardino et al. 1981) and is less invasive than angiography.Angiograms may still be required, however, if arterial embolization is considered as part ofthe treatment of an inoperable lesion (Allison 1978).

In a study at the Royal Marsden Hospital a prediction of resectability based on the CTappearances was correct in 22 of 24 patients (92%) (Golding & Husband 1982). Thus, CT isthe most effective technique available for determining resectability and patients withinoperable tumours may be spared an unnecessary operation.

Is there distant spread?Investigation for distant metastases is an essential step in the preoperative staging of tumours.Most sarcomas metastasize to the lungs. CT is superior to whole lung tomography in thedetection of pulmonary metastases (Muhm et al. 1978, Husband et al. 1981) and it is thereforethe investigation of choice when the chest radiograph is normal, It is also indicated when thechest radiograph shows an apparently single metastasis and resection of this is considered,since the demonstration of further metastases (Figure 8) precludes surgery (Golding .&Husband 1982).

Other distant metastases are uncommon in soft tissue sarcomas. Lymph node dep'osits arelimited mainly to tumours of synovial, muscular or neuronal origin (Tallroth 1976, Dillon &Parkin 1978) and it is our recommendation that in these tumours the abdomen and regionallymph nodes should be included in the examination when CT is used to assess the primary

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Figure 7. Synovial sarcoma of right thigh. A: Right femoral arteriogram showing the tumour circulation in theproximal thigh medially (arrows). B: Phlebogram showing very poor opacification of the femoral vein (arrows) withgood filling of superficial collateral veins. c: Ultrasonogram. A longitudinal section of the thigh shows the tumour(arrows) with the femoral artery (A) stretched over its superficial surface. Although all the margins of the mass arenot shown on this section, the tumour has a similar echo pattern to that shown in Figure 2. D: CT scan showing thetumour (arrows) lying anteromedial to the right femur. E: CT scan during contrast medium infusion into a peripheralvein distal to the tumour. There is enlargement of the femoral vein and the contrast medium is confined to a thincrescent (arrows) around a tumour thrombus. Findings confirmed at surgery. (Figure 7c is reproduced by kindpermission of Dr Brian Gompels; Figures 7D & E reproduced from Husband & Fry 1981, by kind permi$sion)

734 Journal of the Royal SocietI' of Medicine Volunme 75 September 1982

Figure 8. Epithelioid sarcoma of right buttock. CT scan of

L the chest showing multiple pulmonary metastases. The'li chest radiograph showed a large metastasis (M) adjacent

-, v.to the left hilum but did not reveal the small nodules in theright lung (arrows)

tumour and the chest. It should be remembered, however, that CT demonstrates enlargednodes only and that lymphography is required to show small metastases in normal-sizedlymph nodes. Skeletal scintigraphy is the investigation of choice in suspected skeletalmetastases (McKillop & McDougall 1980) and may also detect erosion of bone adjacent tothe primary tumour (Simon & Enneking 1976). Cerebral metastases are best demonstrated byCT (Paxton & Ambrose 1974) and although CT and ultrasound appear comparable in thedetection of hepatic metastases, ultrasound is more readily available than CT.

ConclusionsFor an imaging technique to be valuable in practice it must be both reliable and generallyavailable. While CT services are limited at present, it is our belief that the superiorinformation obtained makes CT mandatory in the investigation of these tumours. When CT isadded to the investigation scheme in this way the clinical management may be changed inmore than 30%O of patients (Golding & Husband 1982). The cross-sectional display given byCT is also valuable for assessing the response of inoperable tumours to treatment, includingthose tumours which involve bone but have a large extraosseous component. In our ownseries CT has also proved valuable in demonstrating or excluding recurrent disease.

In our view plain radiography of thoracic or limb tumours should always be carried out,since the demonstration of bone erosion indicates inoperability without further investigation.In the abdomen, ultrasound is the technique of choice. CT should then be used to assess theextent and operability of the tumour and the examination should include opacification oflocal vessels. CT of the chest is indicated if the chest radiograph is normal or if thoracotomy isconsidered for an apparently single metastasis.

Although skeletal metastases are uncommon, skeletal scintigraphy is a noninvasiveinve-stigation and should, we feel, be carried out in all patients. Examination for other formsof metastasis should probably be dictated by the clinical findings.A diagnostic regime such as the one described permits rapid and accurate diagnosis and

assessment of these tumours, benefiting the patient both by the avoidance of unnecessarysurgery and by speedy and effective treatment planning. Imaging techniques have made greatadvances in the last few years and it is probable that continuing developments and furtherexperience will allow radiologists to make an even greater contribution to patient care.

Acknowledgments: We are grateful to the clinicians who have referred these patients to us, inparticular Dr C L Harmer, Dr E Wiltshaw, Mr J A McKinna and their colleagues in the JointSarcoma Clinic at the Royal Marsden Hospital and also to our colleagues in the Departmentof Radiology. The CT Unit is funded by the Cancer Research Campaign, who also supportone of us (SJG), and the Department of Health and Social Security. Thanks are also due toMrs Jane Brooks and Mrs Janice O'Donnell.

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