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Judy S. Blebea, MD

Bone Tumors

1. What radiographic features should be considered when evaluating a suspected bone

tumor?

When evaluating a suspected bone tumor, morphologic features, periosteal reaction, location in a bone (epiphysis,

metaphysis, diaphysis), distribution within the skeleton (axial vs. appendicular), presence of tumor matrix, and soft tissue

mass should be considered. Morphologic features to consider are the pattern of bone destruction and the size, shape,

margins, and zone of transition of the lesion. A lesion with a sharp border suggests a nonaggressive or benign lesion,

whereas a poorly defined margin, especially one associated with cortical destruction, favors malignancy. Periosteal

reaction reflects the rate of growth of the underlying lesion. Slow-growing lesions may produce a laminated periosteal

reaction with uniform, wavy layers. Malignant lesions that grow in spurts can produce an “onion-skin” pattern, whereas

aggressive lesions with rapid growth are associated with a “sunburst” or “hair-on-end” periosteal reaction. Codman

triangle is the uplifting of the periosteum in a triangular configuration and can be seen with benign and malignant

lesions.

2. How do cartilage tumor matrix and neoplastic bone matrix differ?

Cartilage matrix is typically ringlike, flocculent, or flecklike—in the shape of rings and arcs—whereas

neoplastic bone matrix is typically cloudlike, amorphous, or ivory-like. The detection of tumor matrix can be

helpful in recognizing the etiologic factor of the underlying lesion—that is, whether it is osseous or cartilaginous

in origin.

3. Which imaging study is most useful in arriving at an accurate differential diagnosis

for a bone tumor?

Plain radiography is the first step in detecting and diagnosing a bone tumor. Plain films should also be obtained

initially, even with suspected soft tissue tumors, to identify possible underlying bone involvement or the presence

of calcifications.

4. What is the role of magnetic resonance imaging (MRI) and computed tomography

(CT) in the evaluation of musculoskeletal tumors?

MRI is the most important diagnostic test for local staging and preoperative planning of primary bone and soft tissue

tumors. It is also useful for monitoring the response to chemotherapy or radiation therapy and detecting postoperative

tumor recurrence. CT may be helpful in the detection of tumor matrix and the location of the nidus in a suspected

osteoid osteoma. CT is also used for percutaneous image-guided biopsy of bone tumors.

5. What are some tumor features evaluated with MRI? Can MRI be used to distinguish

between benign and malignant tumors?

The tumor location, extent, and relationship to the neurovascular bundle and the presence of skip lesions and

joint involvement are important features that are assessed with MRI and help to determine the stage of the

tumor and to plan a surgical approach. Although MRI may help in the assessment of the aggressiveness of a

lesion and in the recognition of certain “pathognomonic” lesions, it cannot be used to distinguish reliably between

benign and malignant tumors, and is generally nonspecific in determining tumor cell type. Biopsy of the lesion is

often required.

Key Points: Plain Radiographic Features to Assess for Bone Tumors

1. Morphologic features and pattern of bone destruction, zone of transition

2. Periosteal reaction

3. Location in the bone and distribution in the skeleton

4. Presence of tumor matrix

5. Presence of a soft tissue mass

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Bone Tumors

6. What is the role of intravenous gadolinium contrast enhancement in MRI of

musculoskeletal tumors?

There is some controversy about the need for intravenous contrast enhancement during pretherapy MRI for a patient

with a suspected musculoskeletal tumor. Contrast enhancement may be used to help distinguish tumor margins and

assess tumor vascularity. Its use may also help distinguish malignant viable tissue from inflammatory changes and

necrosis for preoperative biopsy planning. For a follow-up or post-therapy MRI evaluation, contrast enhancement can be

helpful to assess the patient’s response to chemotherapy, to determine the presence of a fluid collection postoperatively,

and to detect tumor recurrence.

7. What is the staging system adopted by the Musculoskeletal Tumor Society, and what

three features form the basis of this staging system?

The Musculoskeletal Tumor Society has adopted the Enneking staging system. Grade, local extent, and presence of

metastases are the three features assessed with this system.

8. Which primary bone tumors tend

to involve the epiphysis most

commonly?

Chondroblastoma and giant cell tumors tend

to involve the epiphysis most commonly.

Chondroblastoma is a benign lesion that is typically

well defined and located in the epiphysis. Although

benign, chondroblastomas can be locally invasive

and metastasize to the lungs. A giant cell tumor

usually arises in the metaphyseal region and

extends to involve the epiphysis. Giant cell tumors

are eccentrically located lesions with a nonsclerotic

zone of transition that typically occurs after

closure of the growth plate (

Fig. 42-1

). A clear cell

chondrosarcoma may also occur in the epiphyseal

region.

9. What is the difference between a

nonossifying fibroma and a fibrous

cortical defect?

Both entities are benign, usually asymptomatic,

well-defined cortical-based lesions with sclerotic

borders seen in the metaphysis or diametaphysis

of long bones, and are identical in their histology.

They differ only in size. Fibrous cortical defects are

smaller (<2 cm), whereas nonossifying fibromas

are larger (>2 cm); both are usually detected

incidentally on radiographs in children and often

subsequently heal with sclerosis.

10. What is the most common malignant tumor involving the skeleton?

Metastases are the most common malignant skeletal tumors.

11. What is the most common primary malignant bone tumor in adults?

Multiple myeloma represents approximately 1% of all malignant diseases and about 10% to 15% of hematologic

malignancies. The excessive proliferation of abnormal plasma cells can result in the formation of a single lesion

(plasmacytoma) or multiple lesions (multiple myeloma).

Figure 42-1.

Plain film anteroposterior radiograph of the ankle shows

a geographic lesion that extends to the epiphyseal region in the distal

tibia. In this patient with closed growth plates, the most likely diagnosis

is giant cell tumor.

Key Points: Primary Bone Tumors in the Epiphyseal Region

1. Chondroblastoma

2. Giant cell tumor

3. Clear cell chondrosarcoma

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musculoskeleTal radiology

12. If the diagnosis of multiple myeloma is suspected, what radiographic evaluation

should be performed?

A skeletal survey is usually obtained. Approximately 75% of patients with multiple myeloma have positive radiographic

findings with “punched-out” osteolytic lesions that have discrete margins and uniform size. Multiple compression

fractures can also be seen. MRI is very sensitive for detecting the presence of marrow lesions and may help in

determining tumor extent.

13. What are the most common primary neoplasms that metastasize to bone?

A few primary tumors account for most metastatic bone lesions. Cancers most likely to metastasize to bone

include prostate, breast, kidney, thyroid, and lung, and are remembered by the mnemonic PB (lead) KetTLe. Other

primary tumors that can metastasize to bone include colon, rectum, stomach, and bladder. The axial skeleton is

seeded more than the appendicular skeleton because of the presence of red bone marrow. It is rare to have bone

metastases below the elbow or knee. Lytic bone metastases must have destroyed 30% to 50% of the bone to

be seen on radiographs. Nuclear medicine bone scans are more sensitive than radiographs for the detection of

metastatic bone disease.

14. Which tumors can give rise to lytic, expansile, “blown-out” metastases of bone?

Bone metastases from renal cell carcinoma and thyroid cancer can show this pattern. Bone metastases from malignant

melanoma may be expansile as well.

15. What is the second most common primary bone tumor after multiple myeloma?

Osteosarcoma is the second most common primary bone tumor after multiple myeloma (

Fig. 42-2

). About 75% of

osteosarcoma lesions occur around the knee and typically arise in the metaphyseal region. The peak incidence is in the

second and third decades, and there is a smaller second peak in patients older than 50 years; this later peak has more

pelvic and craniofacial involvement. Osteosarcoma can develop after radiation exposure, with an average latent period

of 11 years.

16. Which type of tumor can manifest with bone pain,

swelling, tenderness, fever, and increased sedimentation

rate, mimicking an infection?

Ewing sarcoma is a malignant round cell tumor with a predilection for the long

bones and pelvis. Plain films may show a permeative or moth-eaten pattern

of bone destruction with an onion-skin type of periosteal reaction and an

associated soft tissue mass.

17. Where do sarcomas most commonly metastasize?

Sarcomas tend to undergo hematogenous spread, with pulmonary metastases

being the most common.

18. What is the most common benign skeletal neoplasm?

Osteochondroma is the most common benign skeletal neoplasm (

Fig. 42-3

).

This lesion accounts for 20% to 50% of benign bone tumors and 10% to 15%

of all bone tumors. Osteochondromas occur most commonly in the first 2

decades of life, arise from the metaphysis pointing away from the joint, and can

be either flattened (sessile) or stalklike. There is usually cessation of growth of

the osteochondroma after closure of the growth plate. Osteochondromas can

occur after radiation therapy in children and may present with pain because of

mechanical irritation or fracture.

Figure 42-2.

Plain film radiograph shows exuberant bone formation in

this osteosarcoma.

Figure 42-3.

A sessile bony

protuberance is noted arising from the

femur on this plain film radiograph;

this represents an osteochondroma.

Osteochondromas are the most common

benign skeletal neoplasm.

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Bone Tumors

19. Which clinical and radiographic

features suggest malignant

degeneration of an

osteochondroma?

Features suggesting malignant degeneration

include pain, growth after closure of the growth

plate, bony destruction, thickened cartilage

cap, and soft tissue mass. The risk of malignant

transformation of a solitary osteochondroma is

approximately 1%, whereas the risk of hereditary

multiple osteochondromatosis is much higher

and may be 25% to 30%. A sessile lesion is

more likely to degenerate, usually undergoing

malignant transformation to a chondrosarcoma

(

Fig. 42-4

).

20. What is the most common benign

bone tumor of the hand? Where

else may these lesions occur, and

what are the features of malignant

transformation?

An enchondroma is the most common benign

bone tumor of the hand. Small, peripheral

enchondromas of the hand are usually well-

defined lytic lesions that are typically benign,

but may be detected as a result of pathologic

fracture. Solitary enchondromas can also occur

in the long bones and are usually oval in shape

with central calcifications (

Fig. 42-5

). Features

suggestive of malignant degeneration include

an enlarging painful lesion with progressive

destruction of the chondroid matrix and an

expansile soft tissue mass.

21. Which primary bone tumor has the

characteristic history of pain at

night that is relieved by aspirin?

Osteoid osteoma is a primary bone tumor that

has a characteristic history of pain at night that

is relieved by aspirin. The classic radiographic

appearance of this lesion is a round or oval

lucent lesion, which represents the nidus,

that typically measures less than 1 cm and is

surrounded by a zone of bone sclerosis with

cortical thickening.

22. What is fibrous dysplasia?

Fibrous dysplasia is a developmental anomaly of

bone that usually manifests as a solitary lesion

with focal bone expansion, cortical thinning or

thickening, and a “ground-glass” appearance.

Patients with these lesions may be asymptomatic

or present with pathologic fracture. Polyostotic

fibrous dysplasia with associated endocrine

dysfunction that is usually manifested as

precocious female sexual development is known

as McCune-Albright syndrome.

Figure 42-4.

Axial T2-weighted MR image permits the evaluation of

the extent of this biopsy-proven chondrosarcoma. This image is helpful

for staging and preoperative planning.

Figure 42-5.

Anteroposterior view of the femur shows the presence of

cartilage matrix, which is typically ringlike, flocculent, or flecklike, in this

patient with an enchondroma.

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23. Which of the following has an increased incidence of skeletal malignancy: high-dose

radiation therapy, bone infarction, Paget disease, or chronic osteomyelitis?

All of these entities have an increased incidence of skeletal malignancy; osteosarcoma and fibrosarcoma are the most

common forms of malignant degeneration.

24. What is a bone island?

A bone island, or enostosis, is a benign lesion that appears radiographically as an oval or round sclerotic focus that may

have radiating bone spicules from the center of the lesion. Bone islands are typically asymptomatic, are incidentally

discovered, and usually do not show increased radiotracer uptake on a nuclear medicine bone scan.

25. What is the most common location for a skeletal hemangioma?

The most common site of involvement is the spine, particularly the thoracic segment. Most vertebral hemangiomas are

small and asymptomatic, with a coarse, vertical trabecular pattern or corduroy appearance in the vertebral body on plain

films or CT.

B

ibliography

[1] A. Greenspan, Differential Diagnosis of Tumors and Tumor-like Lesions of Bones and Joints, Lippincott Williams & Wilkins, Philadelphia,

1998.

[2] T. Rand, P. Ritschl, S. Trattnig, et al., Imaging of Bone and Soft Tissue Tumors, Springer Verlag, New York, 2001.

[3] D. Resnick, Diagnosis of Bone and Joint Disorders, fourth ed., Saunders, Philadelphia, 2002.

Key Points: Imaging of Bone Tumors

1. Order a plain film first.

2. Use MRI for staging and preoperative planning.

3. Use CT for image-guided biopsy and detection of the nidus of an osteoid

osteoma or pulmonary metastases.

4. Use MRI for follow-up to detect response to therapy or tumor recurrence.