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Postgrad MedJ 1995; 71: 10-16 C) The Fellowship of Postgraduate
Medicine, 1995
Diagnostic dilemmas
The painless soft tissue mass in childhood -tumour or not?
AE Boothroyd, H Carty
Department ofRadiology, RoyalLiverpool Children'sHospital, NHS
Trust,Alder Hey, EatonRoad, LiverpoolL12 2AP, UKAE BoothroydH
Carty
Accepted 30 May 1994
SummarySoft tissue malignancies are uncommonin adults and even
rarer in children.Twelve children presented to the radio-logy
department over a three-year periodwith a clinical diagnosis of a
malignantlower limb mass. This diagnosis wasusually based on the
presence of a firm,painless mass. However, imaging re-vealed a
heterogeneous group of benignpathologies: haemangioma (two
cases),haematoma (two cases), aneurysm (twocases), and one case
each of infection,myositis ossificans, Baker's cyst, lipoma,muscle
rupture, and venous malforma-tion. During the same period there
wasonly one malignant soft tissue neoplasm.A variety of imaging
techniques wereused but ultrasound combined with col-our flow
Doppler was the single mosthelpful modality. The radiological
diag-nosis were confirmed by biopsy, surgeryor clinical
follow-up.
Keywords: childhood, soft tissue mass, CT
scanning,ultrasound
Introduction
When a firm, painless mass is detected, theclinical concern is
usually of a malignanttumour. However, malignant causes of such
amass are much less common in children than inadults. Soft tissue
sarcomas account for only6% of all malignant neoplasms in children
lessthan 15 years of age. Rhabdomyosarcomaaccounts for 53%0 of
these cases.' A review of135 cases of paediatric superficial
massesrevealed only 18 malignancies.2
It is important to consider the possibility ofbenign pathology
(see box), particularly inchildren in whom an episode of trauma
mayhave been forgotten. A careful clinical historyand appropriate
imaging often allows a specificdiagnosis and early alleviation of
anxiety.
In some cases the radiological appearancesmay prove more
reliable than histology, asshown in Case 8, in which the radiology
showedmyositis ossificans but the histology was re-ported as
osteogenic sarcoma. This pitfall hasbeen previusly documented,3 but
it is imporantto emphasise the problems with histology inthis
situation to avoid unnecessary radicalsurgery.
Materials and methods
A total of 12 children who presented forinvestigation of a
clinically suspected soft tissuemalignancy of the lower extremity
are de-scribed. The age range of the group was 15months to 17
years. There were nine boys andthree girls. The children were
investigatedusing a variety of imaging modalities usuallycommencing
with a plain film and ultrasound.
Results
Brief clinical case reports and the findings onimaging are
outlined below:
Case 1A 10-year-old girl sustained a head injury and afractured
right femur in a road traffic accident.One month later a tense
swelling of the right
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Painless soft tissue mass in childhood
thigh was noted. Even though there had been ahistory of trauma,
a malignant mass was sus-pected clinically. Benign pathology was
notconsidered. Angiography revealed a falseaneurysm of the right
superficial femoral artery(fig 1). Diagnosis: aneurysm.
Case 2A 10-year-old girl presented with a firm mass inthe right
thigh. There was no history oftrauma.Contrast enhanced computed
tomography(CT) revealed a true aneurysm of thesuperficial femoral
artery (fig 2). No cause forthis has been identified. Diagnosis:
aneurysm.
Case 3A 10-year-old boy presented with a mass in theleft
buttock. It was initially aspirated andaltered blood obtained. He
was lost to follow upbut re-appeared three years later with a
recur-rence of the mass. CT was performed becauseof a persistent
hard mass and a low attenuation,non-enhancing mass was found
adjacent to theleft ischial tuberosity involving several
musclegroups (fig 3). This was confirmed to be aresolving haematoma
on biopsy and is pre-sumed to be due to bleeding into an
arterio-venous malformation. Further investigationhas been refused.
Diagnosis: haematoma.
Case 4A 3-year-old boy complained ofa painless massin the left
thigh. Ultrasound revealed a well-defined area of low echogenicity
consistentwith an intramuscular haematoma (fig 4). Themass resolved
spontaneously. Diagnosis:haematoma.
Case 5A 13-year-old boy complained of a mass in hisright thigh.
Ultrasound showed an echo-poormass with areas ofhigh echogenicity
consistentwith fat. A diagnosis of a mixed lipohaeman-gioma was
made. Clinical management wasconsistent with this diagnosis.
Diagnosis:haemangioma.
Figure 2 Case 2: CT with contrast shows a trueaneurysm ofthe
distal left superficial femoral artery withsome mural thrombus
Figure 3 Case 3: A lobulated, low attenuation masssurrounds the
left ischial tuberosity on the CT scan(arrowheads). Biopsy revealed
a resolving haematoma
Figure 4 Case 4: A well-defined low echogenicity area(H) is seen
adjacent to the femur (F). These ultrasoundappearances are
compatible with a resolving haema-toma
Case 6A 5-year-old boy presented with the suddenappearance of a
mass in his right calf. Ultra-sound revealed a mass with echogenic
areasconsistent with fat and smaller denselyechogenic areas
representing phleboliths inaddition to vessels with low flow on
Doppler.The appearances was consistent with a throm-bosed
haemangioma. This diagnosis was con-firmed at surgery and the
lesion excised.Diagnosis: haemangioma.
Soft tissue mass in children
* sarcoma* haemangioma* haematoma* aneurysm* infection* myositis
ossificans* Baker's cyst* muscle rupture* venous malformation
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Boothroyd, Carty
Figure 6 Case 8: CT confirms that this opacity isintramuscular
and consistent with myositis ossificans
Figure 5 Case 7: Ultrasound shows an ill-defined areaof low
echogenicity which crosses several tissue planes.The appearances
are those of infection
Case 7A 13-year-old boy was noted to have a painlessmass in high
right thigh overlying his hip. Plainfilms revealed a lytic area in
the right femoralneck distant from the mass and a diagnosis of
ahaemangioma was considered. An arteriogramrevealed a 'tumour'
blush but no neovas-culature. Ultrasound was the most
helpfulexamination, showing an irregular, low echo-genicity mass
with loss of the normal tissueplanes (fig 5). An ultrasound-guided
biopsyyielded inflammatory tissue and surgery re-vealed a sterile
abscess, with its origin in thefemoral neck. The abscess had
tracked in-feriorly to present in the thigh.
Diagnosis:infection.
Case 8A 12-year-old boy presented with a 48-hourhistory of a
hard painful mass in his distal leftthigh and a vague history of
previous trauma.The plain films were initially normal. Ultra-sound
showed a low density irregular lesionextending to the medial
ligament of the kneejoint. On CT the mass had both calcified
andlow-density components and was located in themuscles (fig 6).
The lesion was biopsiedbecause of the clinical suspicion
ofmalignancy.The initial histology was a soft tissueosteogenic
sarcoma but further review corre-lated with the radiological
findings of myositisossificans. A plain radiograph two months
latershowed calcification within the mass (fig 7).Diagnosis:
myositis ossificans.
Figure 7 Case 8: A well-defined area of
calcification/ossification lies posterior to the distal femur on
thelateral view of the left knee
Case 9A 17-year-old boy who was in remission fromleukaemia
presented with a sudden onset of apainless mass in the anterior
aspect of his rightthigh. This was noted to vary in size with
thedegree of contraction of quadriceps femoris onultrasound (figs 8
and 9). The appearances wereof a spontaneous partial rupture of the
rectusfemoris muscle. Diagnosis: muscle rupture.
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13
Figure 10 Case 10: Ultrasound shows a well-definedcystic area in
the popliteal fossa consistent with a Baker'scyst
Figures 8 & 9 Case 9: Ultrasound of the mid thighwith the
quadriceps relaxed and contracted showspartial rupture of the
rectus femoris muscle. Arrowsdefine the muscle bulge with
contraction
Case 10A 8-year-old boy complained of difficulty instraightening
his left knee. Clinical examina-tion revealed a firm mass in the
popliteal fossa.Ultrasound showed a well-defined cystic areabut
communication with the joint could not beidentified (fig 10).
However, an arthrogramperformed to exclude a discoid
meniscusrevealed a Baker's cyst (fig 11). Diagnosis:Baker's
cyst.
Figure 11 Case 10: Arthrography confirms the com-munication of
the cyst with the knee joint
Case 11A 10-month-old girl was noted suddenly todevelop a firm
mass on the inner aspect of herright thigh. The plain film showed a
well-defined lucent mass within the soft tissues ofthe thigh (fig
12). This was confirmed to be alipoma by ultrasound which revealed
adiffusely echogenic, well-defined mass (fig 13).However, there was
persistent clinical concernand CT was performed to exclude a soft
tissuecomponent to the mass. This confirmed thatthe lesion was
composed entirely of fat (fig 14).Diagnosis: lipoma.
Painless soft tissue mass in childhood on June 8, 2021 by guest.
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Boothroyd, Carty
Case 12A 3-year-old boy presented with a painful massin the left
calf. CT revealed a heterogenous lowattenuation area with some
contrast enhance-ment (fig 15). The venous phase of a
peripheralarteriogram revealed a predominantly venousmalformation
(fig 16). Partial thrombosis wasconsidered to be the cause of the
acute presen-tation. Diagnosis: venous malformation.
Figure 12 Case 11: A well-defined lucency is seenwithin the soft
tissues of the medial right thigh consis-tent with a lipoma
Figure 15 Case 12: A poorly enhancing area is seenwithin the
muscles of the calf on CT
Figure 13 Case 11: A diffusely echogenic mass isshown on
ultrasound consistent with a lipoma
Figure 16 Case 12: The venous phase of angiographyreveals a
venous malformation within the calf
Figure 14 Case 11: On CT the mass (arrowed) iscomposed entirely
of fat excluding the possibility of aliposarcoma
Imaging protocol for soft tissuemasses
* plain radiography* ultrasound with colour Doppler to
assess
vascularity* MRIorCT
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Painless soft tissue mass in childhood 15
Discussion
Imaging was able to provide a specific diagnosisor used to guide
a percutaneous biopsy in eacho£the 12 cases described. Ultrasound
is an ideal
/imaging technique for the assessment of manymusculoskeletal
lesions in children and hasbeen in use for investigating soft
tissue lesionssince 1975.4 The now available range of probeswith
high resolution and short focus,5-7coupled with colour Doppler
means that manylesions may be accurately diagnosed by ultra-sound
alone, without the need for more expen-sive investigations. The
absence of ionisingradiation, the ability to perform dynamic
scan-ning during movement and muscle contraction,even with minimal
co-operation from a child,makes it an ideal first investigation,
and it canbe supplemented by CT or magnetic resonanceimaging (MRI)
tailored to resolve a specificclinical problem.A suggested imaging
protocol for the child
presenting with a soft tissue mass followingclinical assessment,
is a plain radiograph andultrasound examination with colour Doppler
toassess a lesion's vascularity. In many instancesa firm or
provisional diagnosis is possible withthese investigations. If the
diagnosis is unclearfrom these investigations then MRI or CT
areindicated. The full extent of any lesion mayrequire MRI or CT to
demonstrate the ana-tomical relationships for surgical planning.
Ifthe lesion proves to be a vascular anomaly,therapeutic
embolisation may be a preferredoption to surgery.Rushing into MRI
may lead to diagnostic
difficulty.8'9 MRI, like all other imaging proce-dures, will not
always distinguish betweenbenign and malignant lesions.'0
In general, true aneurysms arise from blunttrauma and false
aneurysms from a penetratinginjury to the wall of the vessel which
may beiatrogenic." 2 In our series, the false aneurysmwas secondary
to a fractured femur and the trueaneurysm presumed to be secondary
to a for-gotten episode of blunt trauma. A falseaneursym may mimic
an aggressive tumour.'3Ultrasound provides an accurate means
ofdiagnosing aneurysms and can distinguishreliably between the two
types.'4The appearance of a haematoma on ultra-
sound varies widely depending on its age. 15 Thelesion is
initially cystic and develops irregularwalls and internal echoes
with organisationbefore reverting to a cystic configuration at 4-
6weeks. The lesions are generally round or ovalwith their long axis
orientated parallel to themuscle bundles.'6 The difficulty in
diagnosis iscaused by the absence of a history of trauma.Many
ofthese haematomas are due to repetitive
trauma and are more frequent in athletic child-ren.
All haemangiomata contain variableamounts of non-vascular tissue
such as fat,smooth muscle, fibrous tissue, myxoid
stroma,haemosiderin, thrombus and even bone.'7"18 Ifthese elements
can be identified together withthe vessels they allow a definitive
diagnosis ofhaemangioma. Extensive infiltration ofmuscu-lature and
peri-lesion oedema correlates withthe aggressiveness of the
lesion.'9 It is alsoimportant to distinguish between haemangio-mata
and vascular malformations, which have adifferent clinical course
and prognosis. Theyhave differing imaging features but can
usuallybe differentiated clinically.20The classical inflammatory
signs of ery-
thema, local warmth and fluctuance may beabsent in a pyomyositis
which is frequently'woody' on palpation. The absence of
inflam-matory signs may be due to a deep-seated lesionor a
transient bacteraemia superimposed ontrauma.2' Ultrasound is helful
in distinguishingcellulitis from osteomyelitis22 and is helpful
indefining atypical soft tissue infection inneonates.23'24
Myositis ossificans is a rare non-neoplastic,reactive lesion.
The clinical and histologicalfeatures can be very worrying.25
Radiologicallyit is possible to follow the lesion's progressionfrom
a soft tissue density, to a stage of calcifi-cation and
ossification, and then to a maturephase with a central lucency and
a rim of bone.Ifmaturation and shrinkage of the lesion do notoccur,
other diagnoses should be considered.3
Lipomata are generally soft masses and pre-sent little
diagnostic difficulty. However, intra-muscular lipomata may harden
with musclecontraction.26 In our case the sudden appear-ance of a
firm mass was thought to be due toherniation ofthe lipoma through a
fascial plane.Lipomata occur commonly in the posteriorcompartment
of the thigh.27 Simple lipomatahave a uniform matrix of fat density
on CTwhereas liposarcomata usually show prominentareas of soft
tissue density.28'29None of the lesions in this series was
investi-
gated by MRI. This was not easily availableand it was felt that
adequate diagnostic inform-ation had been obtained by the other
tech-niques.We found ultrasound combined with colour
Doppler to be the most helpful initial imagingmodality and used
this to guide further imagingand the most appropriate site for
biopsy.
We would like to thank Mr J Walsh for his helpfulcomments and
Mrs D Turner for typing the manu-script.
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