Common Bone Tumours

This is an enormous topic, one that fills entire textbooks, but bone tumours are certainly seen in the foot, so we'll discuss the topic briefly.  But first, a few words you should know:

Many people panic when they hear the word "tumour".  People often immediately assume the word means cancer.  But it does not.  The word simply means an abnormal bone growth.  So while a tumour may be cancerous, most tumours are not.  The word "malignant" is another word for cancerous.  The word "benign" is another word for non-cancerous.  The word "primary" refers to tumours that originate within the affected bone.  The word "secondary" refers to tumours that have originated from another site in the body (its Primary location) and spread to the affected bone as a secondary location.  The word osteogenic, osteoblastic or blastic refers to lesions that produce new bone in places it shouldn't be.  The word osteolytic or lytic refers to lesions that thin bone out from areas it normally is located.  

So with a few basic words behind us, let's delve into the world of bone tumours. 

Benign Bone Tumours

The most common benign primary bone tumour in the foot is an osteochondroma.  

An osteoid osteoma is a slow-growing, benign, osteoblastic lesion, though it often has a lytic center.  These lesions may be painful, but in many cases, pain is relieved with aspirin.  They are usually under 2cm in diameter and affect the 10-25 year age group. More common in males. Osteoblastomas are usually considered to be larger versions of osteoid osteomas. 

Chondromas are benign lesions most commonly found in adults 30-40 years of age.  Some patients may exhibit multiple lesions (Ollier's disease), which may be disfiguring, as part of a systemic condition (Mafucci's Syndrome).  These patients may see malignant transformation.  Chondromas are usually removed surgically. 

Chondroblastomas are benign lesions affecting immature cartilage.  Males 10-20 year of age are most commonly affected.  Lesions may be painful, and often demonstrate "chickenwire calcifications".  Lesions are typically cleaned out and packed with bone chips. 

Chondromyxoid Fibromas are rare, lytic lesions that most frequently affect those 10-20 years of age.  These lesions may appear lobular or "bubbly" on X-ray.  They are usually removed surgically. 

Unicameral Bone Cysts are benign, lytic lesions that are rarely painful.  They may be considered abnormally hollow bones.  When painful, it may represent a fracture in the wall of the cyst, and a "fallen fragment sign" represents a chip of a fracture that has fallen to the bottom of the lesion.  The lesions are usually cleaned out surgically and packed with bone.  

Aneurysmal Bone Cysts are cysts filled with unclotted blood.  The lesion may be opened, cleaned out and packed with bone chips, but  cryotherapy or irradiation may be indicated

Intraosseous Ganglions resemble unicamceral bone cysts on X-ray, but intraosseous ganglions are more likely to be painful, and the a synovial cell lining is seen in the excised tissue, which is absent from unicameral bone cysts.  

Malignant Bone Tumours

The most common malignant bone tumours found in the foot did not start there.  They are much more likely to have spread from another location in the body, something known as metastasis.  Malignant lesions are usually osteolytic (involving diminished bone density), and may be painful, particularly if the bone is thinned enough to cause a fracture.  In fact, this is the most common way these lesions are first noticed.  Some of the most common cancerous lesions that may spread to the foot from another location are:

• Retinoblastoma

• Medulloblastoma

• Neuroblastoma

• Rhabodmyosarcoma

• Leukemia

• Lymphoma

• Wilm's Tumour

• Tumours from other organs--the GI tract, lung, skin, for example

• Ewing's Sarcomas are very aggressive malignant lesions, usually seen in those under 20 years of age.  Lesions are typically lytic with multiple layers surrounding the lytic core, something known as an "onionskin" appearance on X-ray.  Amputation may be necessary.   

These lesions are most frequently osteolytic (lesions that thin out the bone on X-ray), but they may be osteogenic (lesions that create new bone).

When the lesion is a primary lesion originating within the bone, the most common types are:

• Chondrosarcoma  This is the 3rd most common primary bone tumour, most commonly affecting males between 40-60.  The tumour is lytic, and it is often painful.  It may lift the covering of the bone (perisoteum), and fill it in with bone, creating something known as a Codman's triangle.  Depending upon the size and extent, amputation may be necessary. 

• Osteosarcoma  This is the single most common primary bone tumour, though it only occurs in the foot about 2% of the time.  Teenage boys are the most frequently-affected group.  Like the chondrosarcoma, an osteosarcoma may exhibit a Codman's triangle.  Osteosarcomas may create a memorable appearance on X-ray through something known as a Sunburst Effect, where the tumour is surrounded by sharp spicules of bone protruding around it--reminiscent of the sun with rays of light extending in all directions. 

• Multiple Myeloma  This is a bone marrow disease, and while usually affecting bones outside the foot, it may develop primarily in the foot. 

• Ewing's Sarcoma While usually occurring somewhere else first, then spreading to the foot, Ewing's Sarcomas may, on occasion, develop in the foot primarily.  Like the chondrosarcoma, Ewing's sarcomas may also exhibit Codman's triangle formation or the Starburst effect.   

I'm including a mention of Paget's disease of bone here, too, as this condition, while normally benign, may demonstrate malignant transformation to an osteosarcoma, chondrosarcoma, fibrosarcoma or fibrous histiocytoma.  For more information on Paget's disease, click on the link. 

Diagnosis

Bone tumours are typically diagnosed on a combination of patient history, physical examination and a variety of imaging studies:

• Radiographs or X-rays are the easiest test to get, and these are often very helpful in diagnosing the disorder.

• CT is useful to determine the spread of the tumour, particularly in the harder portions of the bone. 

• MRI is useful to determine the spread of the tumour, particularly in soft tissues and the softer portions of the bone.

• Bone scans are very sensitive tests, and are used primarily to assess possible spread. 

• Angiography (injecting the patient's arteries with a dye, then performing a special X-ray) may be helpful to visualize "tumour blush", where extra circulation is being routed towards the tumour.

But the most accurate diagnosis is done after the lesion is removed and sent to pathology.  There the pathologist looks at the tumour cells and assesses the nucleus of the cells, the rate the cells are multiplying, the areas of cellular death, and the circulation to the cell. 

For more information about X-rays, CT, MRI, and bone scans, please visit our Medical Imaging Page.