Differences between benign and malignant tumours

Benign tumors are unable to metastasize and generally grow slowly.

Benign Malignant
Well defined margin Poorly defined margin
Slow growth Rapid growth
No metastases Distant metastases


Simple bone cyst

Simple bone cyst This is a common bone tumor in children and may lead to pathological fractures. If it is painful, the cause is usually mechanical stress ( pre fracture stage) and symptomatic lesions should be treated. Simple bone cyst illustration: Click to enlarge
Cysts in the region of the hip are particularly prone to fracture.
Characteristics Simple bone cyst
  • Children
  • Mildly Expansile
  • Filled with serous fluid
  • Migrate to diaphysis
  • Path. fractures common


Symptomatic or cysts in high stress areas such as the femur neck need treatment The cyst needs to be decompressed. Methods such as curettage and bone graft, injection with cortisone and simple drilling with K wires are all effective. Fractures through a cyst are treated conservatively ( plaster cast). In high stress areas such as the hip, internal fixation is needed. The cyst usually resolves after the fracture unites.
If a cyst recurs a biopsy is needed, as the diagnosis may be a more aggressive entity such as the aneurismal bone cyst.

Aneurysmal Bone Cyst

Is a cystic expansile bone tumor seen in the first and second decades. It may appear in any bone.
Aneurysmal Bone Cyst of the clavicle Aneurysmal bone cyst of the clavicle.
Expansile bone cyst, loculated
The cyst is filled with blood. 30% are associated or contain elements of another ABC illustration: Click to enlarge
primary lesion such as a GCT, chondroblastoma, fibrous dysplasia, chondro myxoid fibroma, EG, simple cyst, osteoblastoma, non ossifying fibroma The ABC can become large, and can also be the cause of a pathological fracture. Some ABC 's can be fast growing and locally aggressive. Biopsy and histological diagnosis is mandatory if ABC is suspected. Treatment is by curettage and packing with bone chips.
An ABC in the spinous process Commonly seen in the vertebrae, the ABC usually involves the posterior elements.

View Aneurysmal Bone Cyst Screencast videoOnline Video


A benign cartilaginous lesion appearing in adult life, seen often in short tubular bones e.g. the hand. The lesions are usually single but may be multiple.
  • Age: 2nd - 5th decade
  • Cartilage
  • Short cylindrical bones,often in hand
  • Problem: ? Low Grade Chondrosarcoma

X-rays show scalloped erosions on endosteal surface. There may be flecks of calcification. In multiple enchondromatosis (Ollier's disease) there may be associated deformities, such as genu varus or valgus. In the systemic form (Ollier's), there is a high (10 -20%) incidence of malignant transformation.
Ollier's Disease
Multiple enchondromata or Ollier's disease

Treatment is by curettage and bone grafting. Because many of these may be low grade malignant chondrosarcoma ( which is difficult to distinguish histologically from benign enchondroma) additional techniques, such as cryosurgery are also added to make sure the residual cells are killed.



Non Ossifying Fibroma

Non Ossifying Fibroma
Fibrous cortical defect
X-ray features
Margin well defined,
sometimes scalloped,
and often sclerotic.
This is also known as a fibrous cortical defect or a metaphyseal fibrous defect. Occurs in the metaphysis in the first two decades of life. Histologically it consists of fibrous tissue.It is often NOF illustration: Click to enlarge
primary lesion such as a GCT, chondroblastoma, fibrous dysplasia, asymptomatic and found incidentally on X-rays Large lesions may cause a pathological fracture.

Treatment is only required in a symptomatic lesion. The defect is curetted and packed with bone. Fracture through a large Non Ossifying FibromaIf found incidentally on x rays and the lesion is small, leave it alone. Larger lesions are rare, but if > 50% of diameter of the bone consider surgery, as pathological fractures can take place.

Fibrous dysplasia

Histologically also fibrous tissue. Is a more severe and often systemic form non osFibrous Dysplasiasifying fibroma. It begins in childhood and affects one (monostotic) or many bones. It may cause deformities such as coxa vara and facial deformities.
X-ray features
Radio lucent or opaque lesions may be lobular or scalloped. The cortex is eroded and expanded.

Osteoid Osteoma

Osteoid osteoma presents as a sclerotic cortical lesion. It is painful and the pain is relieved by asprin

There is an oval lytic centre known as the nidus. It is this center that produces benign osteoid.

Osteiod osteoma
Osteoid Osteoma of femoral neck. Notice the sclerosis of the neck and the central nidus

Histology -nidus
Histology - the nidus produces osteoid it may contain giant cells

    Differential diagnosis of a sclerotic cortical lesion in a child
  • Osteoid osteoma
  • Stress fracture
  • Chronic osteomyelitis
  • Malignant tumor e.g. osteosarcoma

To locate the nidus computer tomogrammes are helpful. A technetium scan will show a hot spot. Excision of the nidus will cure the pain. An en block excision is done.


The osteochondroma is common and presents as a bony outgrowth near an epiphysis.
Multiple osteochondromas
Lesions be single or multiple. It consists of a bony outgrowth with a cartilage cap. The lesion may have a narrow neck (pedunculated) or may have a broad base (sessile) Growth stops with skeletal growth. If the lesion enlarges the cartilage becomes thickened in adult life consider malignant change in your diagnosis. Malignant change to osteosarcoma or chondrosarcoma may occur in up to 10% of multiple osteochondromas.
    Causes of pain in an Osteochondroma
  • Mechanical eg ileotibial band impingement
  • Fracture
  • Malignant change

Management Not all lesions require excision. Excise symptomatic lesions and do histology. In multiple osteochondroatosis yearly technetium scans are done and hot lesions are excised. All symptomatic lesions must be excised.

Giant Cell Tumours

The Giant Cell Tumor grows in the epiphysis of adults and undermines the mechanical integrity of the joint.
Giant Cell Tumor
Giant Cell Tumour

The GCT consists of giant cells in a spindle cell stroma. The often breaks through the bone and invades the soft tissue. GCT illustration: Click to enlarge
primary lesion such as a GCT, chondroblastoma, fibrous dysplasia, On rare occasions it metastasizes to the lungs. The tumor is curetted and packed with bone. This may fail if it is a major joint and block excision may be required with arthrodesis or joint replacement.


The chondroblastoma has a predilection for the epiphysis and is almost always found here. It does not stretch to the articular surface as the GCT does.
Chondroblastoma of the humeral epiphysis
- always in the epiphysis, shows areas of calcification
Peak age incidence 10 to 20 yrs. Almost never undergo malignant transformation. Chondroblastoma illustration: Click to enlarge
primary lesion such as a GCT, chondroblastoma, fibrous dysplasia,
Curettage and bone graft.

Chondromyxiod Fibroma

The Chondromyxoid Fibroma is composed of myxoid or primitive cartilage and fibrous tissue. It presents in the second decade or later.
Chondromyxoid Fibroma Chondromyxoid fibroma
Eccentrically situated, may stretch to, but not cross, the growth plate
It has a very sclerotic endosteal border. CMF illustration: Click to enlarge
primary lesion such as a GCT, chondroblastoma, fibrous dysplasia,

Extra capsular marginal excision. Recurrence is rare.



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