iv) Management of benign bone tumours

MINI-SYMPOSIUM: ORTHOPAEDIC ONCOLOGY

(iv) Management of benignbone tumoursRob Pollock

AbstractBenign primary bone tumours are rare, occurring most commonly in skel-

etally immature patients, arising from cartilage or bone. The commonest

locations are the distal femur, proximal tibia and proximal humerus. They

present with pain, swelling or pathological fracture. Diagnosis is by plain

x-rays, MRI scans and a core needle biopsy if indicated. More aggressive

tumours may appear radiologically to be similar to malignant tumours.

Treatment depends on the anatomical location, symptoms, the natural

history of the tumour and the morbidity of treatment and in most cases

involves either simple excision or curettage although occasionally it is

necessary to perform a complete excision using the same principles as

for malignant tumours.

Keywords benign bone tumour; non-neoplastic tumour-like conditions

of bone

Introduction

Primary bone tumours are extremely rare, accounting for only

0.2% of human tumours.1 The majority are benign and affect the

skeletally immature patient but some are difficult to distinguish

from their malignant counterparts, have a significant incidence of

local recurrence and may undergo malignant transformation.

Diagnosis and treatment of bone tumours is complex and

management of this group of patients is best undertaken at

specialist centres in a multidisciplinary setting.

Classification

Two classification systems are commonly used, see Tables 1 and 2.

The first is histological, based on the cell of origin. The second is

more clinically orientated and based on the pattern of behaviour of

the tumour.2

While tumours may arise from chondrocytes, osteoblasts,

osteoclasts, periosteum or soft tissue within bone such as

fat or smooth muscle, some fall into a ‘‘miscellaneous’’ group

and their pathogenesis is unclear. Their behaviour dictates their

clinical presentation, varying from being an incidental finding on

an x-ray in the case of a latent lesion to a rapidly growing, painful

lesion associated with functional loss in the case of an aggressive

lesion. This is reflected in Enneking’s classification.

Aetiology

The aetiology of the vast majority of benign bone tumours is

unclear. Numerous theories have been proposed but none has

Rob Pollock BSc (Hons) FRCS (Tr & Orth) Consultant Orthopaedic Surgeon,

Royal National Orthopaedic Hospital, Stanmore, UK.

ORTHOPAEDICS AND TRAUMA 23:4 24

ever been substantiated except multiple hereditary osteochon-

dromatosis (also known as diaphyseal aclasis) which is inherited

as an autosomal dominant. Two genes are responsible, namely

the EXT 1 and EXT 2 genes found at the 8q24 and 11p11-12 loci

respectively. Approximately 15% of patients with osteochon-

dromas have the inherited form of the condition.

Clinical features

The clinical features are non-specific and variable. Some long

standing lesions present as an incidental finding. For example, an

adolescent who attends the accident and emergency department

after a knee injury and a fibrous cortical defect is found on X-ray

(Figure 1). Some tumours such as osteochondroma present with

a long history of a painless swelling (Figure 2), but more

aggressive lesions, such as giant cell tumour, usually present

with a short history of a pain, swelling and loss of function.

Investigation

As some benign bone tumours can be difficult to distinguish from

their malignant counterparts, investigation should be carried out

in a multidisciplinary setting, ideally in a specialist musculo-

skeletal tumour centre.3 The bare minimum is adequate imaging

by plain x-ray and a magnetic resonance imaging (MRI) scan.

The radiological features may be so clear that, if compatible with

the clinical picture, tissue diagnosis is not necessary before

definitive treatment. However, if there is any doubt about the

diagnosis, a tissue diagnosis should be obtained, which is best

done by core needle biopsy using a Jamshedi needle.

Management

General principles

Treatment is dependant on many factors, particularly:

� patient’s symptoms

� natural history of the tumour

� morbidity of treatment.

Treatment varies from simple observation with repeat

imaging through to wide excision using the same surgical

principles as for malignant tumours. When treating bone

tumours the surgeon has to balance excision margin against

function. With wider margins, there may be greater functional

loss but a lesser chance of local recurrence. Conversely, intra-

lesional surgery has less morbidity but a greater risk of local

recurrence.

Non-operative

Asymptomatic lesions that fall into the Enneking latent group of

tumours can simply be observed, for example the natural history

of lesions such as non-ossifying fibromas and is well documented

and predictable and it is safe to leave them alone. If the diagnosis

has been made on imaging alone and non-operative treatment

has been chosen, obviously histological confirmation of the

diagnosis is not going to be available. Thus it is advisable to

repeat the plain x-ray after three to six months to ensure that the

tumour is showing no signs of progression. If radiological or

clinical progression does occur, then there must be a low

threshold for biopsy.

8 � 2009 Elsevier Ltd. All rights reserved.


Curettage

Curettage is the treatment of choice for the majority of benign

bone tumours requiring surgical intervention. It is, by definition,

intralesional surgery. The intention is to achieve macroscopically

clear margins, accepting that microscopic disease is likely to be

left behind.

The technique involves exposing the affected bone and

creating a bone window with osteotomes. The window needs to

be big enough to obtain an adequate view of the tumour but

small enough to ensure that the grafting material can be con-

tained within the bone at the end of the procedure. It is helpful to

use an image intensifier per-operatively to ensure that the

curettage has cleared the entire lesion.

After curettage, dependant on the histology of the tumour, its

anatomical location of the tumour, the age of the patient, the

Classification of tumour by histological subtype

Cell type Tumour subtype

Chondrocyte Enchondroma

Osteochondroma

Chondroblastoma

Chondromyxoid fibroma

Osteoblast Osteoid osteoma

Osteoblastoma

Osteoclast Giant cell tumour

Periosteum Periosteal chondroma

Bizarre periosteal

osteochondromatous proliferation

Vascular Haemangioma

Fat Lipoma

Smooth muscle Leiomyoma

Miscellaneous Simple bone cyst

Aneurysmal bone cyst

Langerhans cell histiocytosis

Fibrous dysplasia

Osteofibrous dysplasia

Fibrous cortical defect

Non ossifying fibroma

Table 1


likelihood of local recurrence and the risk of pathological frac-

ture, the resulting cavity may be left unfilled or filled with iliac

crest autograft, morcellised allograft, synthetic bone substitute or

polymethylmethacrylate cement (PMMA). Additionally, the

curetted bone can be augmented with internal fixation to prevent

a pathological fracture (Figure 4).

After curettage some tumours have a higher incidence of local

recurrence than others, such as giant cell tumours, osteo-

blastomas, chondroblastomas and aneurysmal bone cysts. When

treating these, it has been shown that using some form of

Figure 1 Fibrous cortical defect in the medial aspect of the proximal tibia.

Classification of tumour by biological behaviour according to Enneking2

Classification Behaviour Example of tumour

Latent Slow growth with spontaneous healing. Often incidental

finding on x-ray. No treatment required

Fibrous cortical defect, non ossifying fibroma,

Active Progressive growth over time and usually symptomatic.

Treatment of choice; curettage. Low incidence of local recurrence

Chondromyxoid fibroma, enchondroma, LCH,

simple bone cyst

Aggressive Rapid growth of tumour often extending beyond periosteum into

the soft tissues. Treatment of choice curettage or excision.

10e15% chance of local recurrence

Chondroblastoma, osteoblastoma, giant

cell tumour, aneurysmal bone cyst

Table 2

� 2009 Elsevier Ltd. All rights reserved.


adjuvant treatment reduces the risk of local recurrence.4 These

include treating the cavity wall with a high speed burr, phenol,

hydrogen peroxide or liquid nitrogen and filling the defect with

PMMA. Which of these adjuvants is used depends on the sur-

geon’s preference, but the incidence of local recurrence after

curettage of these more aggressive tumours is 10e15% even with

adjuvant treatment.

Radiofrequency ablation (RFA)

RFA is the technique of choice for small, symptomatic lesions

less than 1.5 cm in diameter e.g. osteoid osteomas. It causes

Figure 2 Osteochondroma arising from the medial aspect of the right

distal femur. This presented as a painless lump with symptoms of

impingement on the hamstring tendons.

Curettage practice points

C Intralesional surgery leaving residual microscopic disease

C Image intensifier ensures clearance of tumour

C Adjuvant treatment to cavity reduces incidence of local

recurrence

C Choice of filler depends on histology, location of tumour, age

of patient and risk of fracture

C Internal fixation strengthens construct and helps prevent

pathological fracture


targeted thermal destruction of bone (Figure 3). Under general

anaesthesia, guided by computerized tomography (CT),

a Jamshedi needle is inserted percutaneously into the centre of

the lesion. The radiofrequency wire is then passed down the

needle and its position checked. When the device is switched on,

heat is generated at the tip of the wire using microwave energy.

The target temperature is 80e90 degrees Celsius and the duration

of treatment is typically five to ten minutes. For lesions greater

than 1 cm. in diameter two probes can be used.

The advantage of RFA is that the tumour is treated with

minimal destruction of surrounding bone and permits treatment

of tumours in surgically inaccessible locations with minimal

morbidity. In reality, the perceived disadvantage that a tissue

diagnosis is rarely obtained doesn’t matter as the diagnosis is

clear cut both clinically and radiologically.

Excision and reconstruction

Complete excision of a benign bone tumour is indicated when the

tumour is particularly aggressive. This may manifest as bone

expansion, bone destruction, extra-osseous extension of disease,

a CT scan showing an osteoid osteoma in the femoral head. b CT

guided radiofrequency ablation.

Figure 3



pathological fracture or combinations of the above. If the tumour

is subarticular, there may even be no alternative but to sacrifice

the joint.

aPlain x-ray showingahaemangiomaof theproximal femur. Thepatient

is at risk of pathological fracture. b Post-operative x-ray following

curettage and internal fixationwith a dynamic condylar screwandplate.

Figure 4


The surgical principles are similar to those used when treating

a malignant bone tumour. The intention is to perform a marginal

but complete excision and remove both macroscopic and

microscopic disease. After a section of bone has been excised,

some form of reconstruction will be necessary, which may be

a biological reconstruction such as a vascularised fibula graft or

a massive endoprosthesis (Figure 5). The reconstruction used is

dependant on many factors, particularly anatomical location and

the individual surgeon’s preferences.

Management of specific tumours

Cartilage tumours

Osteochondroma (synonym: exostosis) Osteochondromas are

cartilage capped bony projections with a marrow cavity contin-

uous with the underlying bone. They account for approximately

35% of all benign bone tumours and present within the first three

decades of life.5 Most occur close to the physis of long bones but

they can also arise from flat bones such as the scapula and pelvis.

The commonest sites are the distal femur and proximal tibia,

followed by the proximal humerus and proximal fibula. Symp-

toms are most commonly mechanical and caused by impinge-

ment of the osteochondroma on nearby tendons, especially

around the knee.

In about 15% of cases they are multiple, a condition known as

diaphyseal aclasis (Figure 6), which in most of cases are familial

and inherited as an autosomal dominant, but sporadic cases are

well recognised. The genetic defect again appears to be in the

tumour suppressor genes EXT1 and EXT2.

Malignant transformation of a solitary osteochondroma into

chondrosarcoma occurs in approximately 1% of cases and up to

3% patients with diaphyseal aclasis.5 The warning signs include

rapid increase in size of an osteochondroma associated with

increasing pain. Of particular concern are pelvic osteochon-

dromas that may be large and silent until they transform. If there

is any suspicion of malignant transformation the osteochon-

droma should be imaged with an MRI scan and the cartilage cap

assessed. Cartilage caps greater than 1 cm suggest a high prob-

ability of malignant transformation.

Surgical excision of osteochondromas is usually curative but it

is important to excise the cartilage cap in its entirety or local

recurrence is likely. In patients with diaphyseal aclasis it is

impractical to excise every osteochondroma and surgery is

reserved for those which are symptomatic, unsightly or which

are suspicious for malignant transformation.

Enchondroma Enchondromas are benign, intramedullary

cartilage neoplasms which account for approximately 10e25% of

all benign bone tumours and present at any age.5 They mainly

affect the long bones and are most commonly solitary. The hands

and feet are most commonly affected followed by the proximal

humerus and proximal and distal femur.

While enchondromas in the larger long bones such as the

humerus or femur may be asymptomatic and discovered inci-

dentally, the most common presentation is with a palpable

swelling on the hands or feet. Pain may or may not be present

and some are associated with a pathological fracture.

The radiological features of enchondromas of the hands and

feet are those of a well defined, radiolucent lesion exhibiting

punctate mineralization, and may be associated with bone



expansion. They are usually ‘‘hot’’ on bone scan. In larger bones

chondral tissue is seen in the metaphyseal region. Lesions greater

than 5 cm in length and causing endosteal scalloping on MRI

should be considered as possible low-grade chondrosarcoma.

The majority of enchondromas are successfully treated with

curettage and the local recurrence rate is extremely low.

Ollier’s disease and Mafucci syndrome Ollier’s disease is

a developmental disorder characterized by multiple

Osteochondroma practice points

C Commonest benign bone tumour

C Most commonly seen in the metaphyseal region of long bones

C Distal femur and proximal tibia are the commonest sites

C 15% cases are multiple

C Autosomal dominant inheritance

C 1% risk of malignant transformation in solitary cases (3% if

multiple)

C Surgical excision if symptomatic, unsightly or suspicious for

malignant transformation


enchondromas in the long bones of the hands, feet and limbs.

When associated with soft tissue or visceral haemangiomas the

condition is known as Mafucci syndrome (Figure 7). The aeti-

ology is unclear; most cases are sporadic rather than inherited.

The condition usually presents in early childhood with lumps in

the hands and feet, limb deformity and/or multiple pathological

fractures.

Diagnosis is based on the clinical picture and x-ray appear-

ances. Treatment is aimed at maintaining function, preventing

deformity and careful surveillance in order to pick up malignant

transformation early. The incidence of malignant transformation

into chondrosarcoma is approximately 15e30% in patients with

Ollier’s and probably even greater in those with Mafucii’s.6

Chondroblastoma Chondroblastoma is a cartilage producing

tumour typically arising in the epiphysis of skeletally immature

patients. There is a slight male preponderance. 75% occur in

long bones and the commonest sites are the proximal and distal

femur, the proximal tibia and the proximal humerus.7

Symptoms vary from mild pain of many years duration to

recent onset of severe pain. Clinically, patients may develop an

effusion in the hip or knee associated with stiffness. Plain x-rays

show a well-defined, lytic lesion within the epiphysis and MRI

a Lateral view of the wrist showing a GCT of the distal radius. b Axial T1 weighted MRI scan showing expansion of the distal radius with cortical

thinning. The extensor tendons are closely applied to the pseudo-capsule of the lesion. c A free, vascularised fibula graft has been inserted with

a paddle of soft tissue to aid wound closure. d One year post-operative x-ray showing complete bone union and successful wrist arthrodesis.

Figure 5



shows a sharply demarcated chondral lesion with surrounding

oedema (Figure 8). Core needle biopsy will confirm the diagnosis.

Curettage is the treatment of choice and is successful in

80e90%.

Chondromyxoid fibroma This is one of the least common bone

tumours. It most commonly affects the long bones, particularly

around the knee, of patients in their second and third decades.

The clinical presentation is very similar to a chondroblastoma

and the treatment and prognosis is also the same.

Bone tumours

Osteoid osteoma This is a small, bone forming tumour which

can occur in any bone but is most commonly seen in the prox-

imal femur (See Figure 3). It usually affects skeletally immature

patients but it is also seen in young adults. Histologically the

features are the same as an osteoblastoma.8

The clinical presentation is classic with a history of constant,

unremitting pain often worse at night, which usually responds to

aspirin and non-steroidal anti-inflammatory drugs (NSAIDs).

The site of the lesion often determines the clinical findings; in

the spine it may cause scoliosis, in fingers it may cause signifi-

cant swelling and loss of function and if the lesion is sub-

articular, it may cause a joint effusion. The differential diagnosis

includes Brodie’s abscess, stress fracture or subtle area of

osteomyelitis.

Figure 6 Classic appearances of diaphyseal aclasis.


They are too small to biopsy and the diagnosis is made on the

basis of clinical presentation and imaging. The findings of scle-

rosis on plain x-ray, high uptake on bone scan or single photon

emission computed tomography (SPECT), a nidus on CT and the

presence of oedema on MRI are enough to make the diagnosis.

The treatment of choice is percutaneous, CT guided radio-

frequency ablation described above.4 The success rate in most

series is 90e95% after a single treatment and 100% after two

treatments. The complication rate is extremely low.9

Osteoblastoma This is a rare, bone forming tumour that typically

affects young adults aged 10e30 years. It is twice as common in

men as women. Over 50% of cases affect the posterior elements

of the spine, pelvis or the sacrum (Figure 9). In the rest of the

skeleton the proximal and distal femur and the proximal tibia are

the commonest sites.10

The clinical features are similar to those of an osteoid osteoma

i.e. chronic pain. Imaging reveals a well defined, lytic lesion

somewhere between 3 and 10 cm in diameter. Some osteo-

blastomas are associated with aneurysmal bone cyst (ABC)

change. Osteoblastomas can be hard to differentiate from oste-

oblastic osteosarcoma and thus core needle biopsy is recom-

mended before definitive treatment is carried out.

The treatment of choice is curettage and cementation. The

prognosis is good and the incidence of local recurrence after

curettage is low.

Figure 7 AP x-ray of the foot showing multiple enchondromas and a hae-

mangioma in the 4th web space. These are the features of Mafuccci

syndrome.



a MRI scan showing the classic appearance of a chondroblastoma. b Post-operative x-ray following curettage.

Figure 8

Giant cell tumour Giant cell tumours (GCT) are locally aggres-

sive lesions which account for about 20% of all benign bone

tumours. They occur in adults between the ages of 20 and 40

years with a slight female preponderance. They affect the meta-

physeal regions of the long bones and are commonest in the

distal femur, proximal tibia, proximal humerus and distal radius.

About 5% of GCTs affect the flat bones especially those of the

pelvis.

Patients usually present with a short history of pain, swelling

and functional loss. Plain x-rays show a lytic lesion with

Figure 9 CT scan of the pelvis showing a lytic lesion in the posterior ilium.

Biopsy confirmed the diagnosis of osteoblastoma and the lesion was

curetted.


a narrow zone of transition extending to the sub-articular

surface. MRI reveals a haemosiderin rich lesion with low to

intermediate signal on T1 weighted images and high intensity on

T2 weighted images (Figure 10). Campanacci classified GCTs

according to their radiological appearance.11

Type 1 or quiescent tumours have a well-defined margin,

surrounding sclerosis and no cortical involvement.

Type 2 or active tumours lack surrounding sclerosis and

demonstrate cortical expansion but are still well-defined.

Type 3 or aggressive tumours have ill-defined margins, show

cortical destruction and extend into the soft tissues.

The differential diagnosis includes hyperparathyroidism,

aneurysmal bone cyst and telangiectatic osteosarcoma and thus

again core needle biopsy is essential.

Treatment of GCTs depends on the anatomical location, the

aggressiveness of the tumour clinically and radiologically, and

the functional expectations of the patient. If the joint can be

saved, the initial treatment of choice is curettage with some form

of adjuvant treatment and cementation with PMMA. If the lesion

is very destructive, i.e. Campanacci type 3 tumour or if there is

a pathological fracture or if a joint is involved then, wide excision

may be necessary. Following a wide excision, tumours around

the knee are best reconstructed with a massive endoprosthesis to

allow immediate weight bearing and early recovery of function.

Tumours around the wrist are better treated with a vascularised

fibula graft with or without wrist fusion12 (See Figure 5).

The incidence of local recurrence after curettage in most series

is 10e15% and usually occurs within the first two years.4,12,13



a Plain x-ray showing a giant cell tumour of the proximal tibia. Note the narrow zone of transition and extension of tumour up to the sub-chondral

region. b MRI scan showing classical appearances of a GCT.

Figure 10

Some studies have suggested that bisphosphonates post-opera-

tively may reduce the incidence of local recurrence.14

Despite them being histologically benign, pulmonary metas-

tases are seen in up to 2% of patients with giant cell tumours, on

average three to four years after diagnosis. Most grow slowly,

some regress and some progress leading to the death of the

patient. True malignant transformation of a giant cell tumour is

extremely rare.

Miscellaneous lesions

Non-ossifying fibroma/fibrous cortical defect By convention,

a fibrous cortical defect measures less than 1 cm in diameter and

a non-ossifying fibroma is larger than 1 cm but histologically

these two conditions are identical (Figure 5). Their aetiology is

GCT practice points

C Locally aggressive

C Distal femur, proximal tibia, proximal humerus, distal radius

C Differential diagnosis ABC, telangiectatic osteosarcoma,

hyperparathyroidism

C Campanacci types 1, 2 & 3

C Treat with curettage and some form of adjuvant

C 10e15% local recurrence rate

C Bisphosphonates may reduce incidence of local recurrence


unclear. They fall into the latent category by Enneking’s classi-

fication and are most commonly seen as an incidental finding in

skeletally immature patients. They are rarely symptomatic and

can be safely observed. Occasionally a large non-ossifying

fibroma can cause a stress fracture in the adjacent bone in which

case curettage and internal fixation are indicated.

Simple bone cyst (synonym: unicameral bone cyst) Simple

bone cysts (SBC) are fluid filled, metaphyseal cysts of unclear

aetiology. They are most commonly seen in the fist two decades

of life with a male to female ratio of 3:1. The proximal femur,

proximal tibia and proximal humerus account for 90% of cases.15

Most patients present with a pathological fracture after

minimal trauma (Figure 11). Plain X-rays are diagnostic and

show a metaphyseal lucency often extending into the diaphysis

but never involving the epiphysis. The cortex is usually thin and

may be mildly expanded but never beyond the width of the

physis. If a fracture is present a ‘‘fallen fragment’’ sign may be

seen.

Numerous methods of treating SBCs have been described

including; aspiration and injection with steroid, injection with

bone marrow, inserting a cannulated screw to decompress the

cyst, fixation with Nancy nails and curettage combined with

internal fixation.16 Even after curettage recurrence rates of

10e20% are reported. By the time the patient is skeletally mature

the cyst will have healed. The treatment modality chosen

depends partly on the anatomical location of the cyst. Cysts of

weight bearing bones such as those in the femoral neck are more



frequently curetted, grafted and internally fixed than those in the

non- weight bearing bones.

Aneurysmal bone cyst Aneurysmal bone cysts (ABC) are mul-

tilocular, expansile, aggressive, destructive lesions that may

expand into the soft tissues. They are most common in the first

two decades of life and typically affect the metaphyseal regions of

the long bones (Figure 12). They can arise de novo or they can

complicate other benign tumours i.e. they show ‘‘ABC change’’.

Most patients present with a short history of pain and

swelling. The characteristic radiological findings are those of an

eccentric, expansile, well-defined, lytic lesion on plain x-ray with

the presence of multiple fluid-fluid levels on MRI. The differential

diagnosis includes giant cell tumour and telangiectatic osteosar-

coma. Biopsy should be attempted although, frequently, only

blood clot is obtained.

The majority of ABCs are suitable for curettage and grafting.

They can be extremely vascular and it is advisable to perform

arteriography and embolisation pre-operatively in lesions where

a tourniquet cannot be used. Local recurrence occurs in

approximately 25% and is usually apparent within a year of

surgery.17 ABCs at the aggressive end of the spectrum may

require marginal but complete excision.

Langerhans cell histiocytosis. (Synonyms: Histiocytosis X,

Eosinophilic granuloma) Langerhans cell histiocytosis (LCH) is

a rare disorder that can affect any bone and be monostotic or

polyostotic. Visceral structures can also be involved. There is

a wide age range from the first to the eighth decade but 80% of

patients are under thirty.

Figure 11 Typical x-ray appearance of a simple bone cyst. Note the mild

expansion but not wider than the physis.


Patients present with pain and swelling and the imaging

features may be aggressive. The differential diagnosis includes

osteomyelitis and Ewing’s sarcoma and thus biopsy is essential.

Treatment varies from surveillance through to curettage and for

those with multiple sites of disease, chemotherapy.

Fibrous dysplasia Fibrous dysplasia (FD) is a developmental

abnormality rather than a tumour and may affect any bone.

Clinical presentation with pain, deformity or pathological frac-

ture can occur at any age. It may be monostotic or polyostotic.

McCune-Albright syndrome is polyostotic FD, pigmented skin

lesions resembling ‘‘the coast of Maine’’ and endocrinopathy.

X-ray appearances are diagnostic showing a ground glass

appearance of the affected bone. ABC change can occur.

Treatment is aimed at symptom control. Bisphosphonates

have been shown to be effective in reducing pain.18 Surgery is

reserved for pathological fractures or severe deformity.

Osteofibrous dysplasia Osteofibrous dysplasia (OFD) is a slow

growing, fibro-osseous lesion classically affecting the cortical

bone of the tibial diaphysis. It is most commonly seen in skele-

tally immature males. Presentation varies from an incidental

finding to a painful deformity. It is usually self limiting and

spontaneous healing often occurs. The differential diagnosis

includes adamantinoma; a low-grade malignant lesion with

similar radiological appearances. Indeed there is controversy as

to whether OFD has the potential to transform into ada-

mantinoma, but others think they are two separate entities. A

Figure 12 Plain x-ray showing an aneurysmal bone cyst. Note that the

bone is expanded beyond the width of the physis.



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FURTHER READING

Fletcher C, Unni K, Mertens F, eds. World Health Organization classification

of tumours. Pathology and genetics of tumours of soft tissue and

bone. Lyon: IARC Press; 2002.

Research directions

C Phase 2 clinical trial studying the use of Denosumab in the

management of GCTs. This agent is a monoclonal antibody

that targets the RANK ligand, part of the signaling pathway

that stimulates osteoblasts

C Use of novel bone substitutes to promote bone healing after

curettage

C Molecular genetic studies to identify genes and chromosomal

aberrations responsible for these tumours


iv) Management of benign bone tumours

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Transcript of iv) Management of benign bone tumours