Benign Bone Tumors and Tumor-Like Conditions The document discusses various benign bone tumors and tumor-like conditions. It describes their histology, locations, imaging appearance and distinguishing characteristics. Some of the key tumors mentioned include osteochondroma, osteoid osteoma, osteoblastoma, enchondroma and chondroblastoma. Plain radiography, CT and MRI are important imaging modalities to evaluate the location, margins, matrix and other characteristics to arrive at a proper diagnosis of benign bone lesions.

1. Benign Bone Tumors and
Tumor Like Conditions
DR PRIYANKA RANA

2. • Bone tumors may be defined as a new growth
arising in a bone or derived from cells which are
components of skeletal tissue.
• The majority of benign true tumor of bone are
detected in children and young adults.
• Benign bone tumors can be classified according to
their matrix production and/ or predominant cell
type into cartilage forming, bone forming, fibrous,
vascular and other connective tissue lesions.
• The term “tumor-like lesions of bone” denotes
various conditions of non-neoplastic nature
originating from or affecting the bone and
presenting as solitary or multiple bone lesions.

3. • Despite availability of a host of imaging
modalities, plain radiographs continue to play a
major role in the diagnostic evaluation of bone
neoplasms. Plain radiographs demonstrate
location of the tumor in the body, segment
involved—whether epiphysis, metaphysis or
diaphysis, growth characters of the lesion such
as margin-well defined/ ill-defined, presence or
absence of periosteal reaction and the
appearance of tumor matrix—whether calcified
or not, which are all important parameters to
arrive at a proper diagnosis.

4. The pointers to the benign nature of a bone tumor include the following:
1. Area of geographic bone destruction which is well circumscribed and is
characterized by a sharp transition between the destroyed area and the
normal bone (i.e. narrow zone of transition—less than 1 cm).
2. Sclerotic margin indicates slow growth and is generally seen in benign
lesions located at the metaphysis. Certain tumors stimulate surrounding
sclerosis which may obscure the central lytic area such as osteoid
osteoma.
3. Periosteal reaction: In general, periosteal reaction is not a feature of
benign bone tumors unless a fracture has occurred except in a very few
lesions such as osteo blastoma, osteoid osteoma and chondromyxoid
fibroma. Periosteal reaction is radiographically described as solid or
interrupted. Solid periosteal reaction is defined as a single layer of new
bone greater than1 mm in thickness which is usually of uniform density.
When seen, solid periosteal reaction indicates benign pathology. It is seen
in osteoid osteoma and osteoblastoma.
4. Tumor matrix: Presence of calcification in the form of rings, patches or
stippled flecks point to the cartilaginous origin of the tumor. A ground
glass haze indicates fibrous lesions. Osteoid matrix is seen in bone forming
tumors.

6. BONE FORMING TUMORS
Enostosis:
• These lesions are commonly known as ‘bony islands’ are
usually asymptomatic.
• Histologically, bone Island consist of dense intramedullary
lamellar bone with normal haversian canals.
• Enostosis are commonly found in spine, ribs and pelvis.
• It is usually seen as oval, densely sclerotic intramedullary
lesions. Usually a bone island is aligned in the long axis of
trabeculae.
• MRI are helpful in the differentiation, as bony islands
usually do not exhibit an increase tracer uptake on bone
scans.
• On MRI, enostosis shows hypointense signal on both T1W
and T2W sequences while sclerotic metastasis shows halo
of surrounding marrow edema on fluid sensitive
sequences.

9. Osteoma
• Histologically, an osteoma is composed of both
dense and woven bone and arises from the cortex.
• Common sites include outer table of skull, paranasal
sinuses (frontal/ ethmoid) and mandible.
• They are generally asymptomatic, but may cause
sinus obstruction, proptosis, etc. Radio- logically,
osteoma is seen as a well circumscribed lesion arises
from the cortex, which protrudes from the surface of
the affected bone.
• It demonstrates same density as cortex on X-ray and
CT scan.
• On MRI, osteoma shows hypointense signal on both
T1 and T2W images. Multiple osteomas occur as a
part of Gardner’s syndrome.

11. Osteoid Osteoma
• Osteoid osteoma is a fairly common tumor, accounting for approximately 10
to 12 percent of all benign tumors.
• These tumors usually affects patients between 5 and 25 years of age.
• Clinically most patients presents with pain that is especially severe at night
and relieved by aspirin or other nonsteroidal anti-inflammatory agents.
• More than half of tumors are located in proximal femur and tibia.
• They occur less frequently in the upper extremities than in the lower
extremities.
• Osteoid osteoma also frequently affect the tubular bones of the hands and
feet. They are however less common in the spine, where they affect the
posterior arches of the vertebrae.
• Histologically, the lesion consists of a nidus which is usually less than 1 cm
in diameter and surrounded by variable degree of sclerotic bone depending
upon location. The nidus contains interlacing trabeculae at various stages of
ossification within a stroma of loose, vascular connective tissue.
• Osteoid osteoma can be cortical (the most common type), cancellous or
medullary, and subperiosteal.The latter two types produce less sclerotic
bone than those in the cortex do, making radiologic diagnosis difficult.

12. • Radiographically, the lesion appears as well defined lytic
lesion, surrounded by reactive sclerosis. Nidus may be purely
radiolucent or contain a dense center. Intra-articular osteoid
osteomas may be either cancellous or periosteal and have little
reactive bone or periosteal new bone formation.
• Computed tomography is very useful in showing the nidus,
which can vary in its degree of ossification. Computed
tomography appears to display the nidus better than MRI.
Intense bone marrow edema adjacent to nidus is very useful to
detect and localized the lesion on MRI however nidus may not
readily visible if it is very small.
• The tumor nidus typically shows hypo to intermediate signal on
T1W images and low to high signal on T2W images.
• The nidus shows enhancement with gadolinium.
• Intra-articular osteoid osteomas produce joint effusions and
synovial proliferation.

14. Osteoblastoma
• Osteoblastoma is rare bone forming tumors and most
commonly occurs in patients in the second and third
decade of life.
• This tumor is more common in males than in females.
• Histologically the osteoblastoma is closely related to
osteoid osteomas except that bony trabeculae are
broader and longer with absence of surrounding sclerotic
halo.
• Size is an important consideration in distinguishing
between these two types of tumors. If the size of lesion is
less than 2 cm in diameter than it is likely of be osteoid
osteomas, whereas tumors larger than 2 cm are usually
osteoblastoma.
• The most common location of osteoblastoma is spine
where it classically affects posterior elements. The other
common locations are proximal femur and talus.

15. • On plain X-ray, spinal osteoblastoma is
osteolytic lesion with destruction of overlying
cortex and may extend to in the spinal canal. In
the long bones osteoblastoma appear
radiologically as round or oval lucent tumors in
the medulla. Periosteal reaction is common.
Computed tomography demonstrate extent of
lesion in complex bony structures like and spine
and pelvis better than radiography.
• Magnetic resonance imaging features may be
nonspecific but helps to determine extension of
vertebral lesion into spinal canal and spinal
foramina.

17. CARTILAGE FORMING TUMORS
Osteochondroma
• Osteochondromas are common lesions of the growing
skeleton.
• It is the most common benign neoplasm and constitutes 20 to
50 percent of all benign tumors.
• They arise from bony metaphysis with cartilage cap covering.
• These tumors are either pedunculated or sessile.
• The long axis of the osteochondroma pedicle or stalk is almost
always directed away from the adjacent joint. The direct
communication between the osteochondroma and the cortex
and marrow cavity of the bone from which it arises is a
distinctive feature, that is particularly well demonstrated on
computed tomography and magnetic resonance imaging.

18. Multiple osteochondroma occur as a manifestation of diaphyseal aclasia, an inherited
disorder with autosomal dominance (Fig.).

20. Enchondroma
• Enchondromas accounts for 12 percent of benign bone
tumors.
• These are most frequently located in the large and small
tubular bones of the hands and feet. Like other cartilaginous
tumors, enchondromas exhibit a lobulated growth pattern,
that results in asymmetric expansion of the medullary cavity
and endosteal scalloping.
• Tumor matrix may be radiolucent or show calcification.
Characteristic cartilaginous ring and arc pattern of
calcifications is seen on radiographs and CT images.
• On MR imaging, the tumor is isointense to muscle on T1-
weighted and exhibits a heterogeneous, predominantly high
T2- weighted signal. Contrast enhanced MRI may
demonstrate a pattern of thin arcs and rings.

21. Ollier’s disease
is a nonheritable
disorder of
cartilage
proliferation in
which
enchondromas
involve multiple
bones,
especially those
of the hands and
may result in
skeletal
deformity.

22. • Enchondromatosis accompanied by multiple
hemangiomas is known as Maffucci’s syndrome.
Calcified phleboliths may be demonstrated
radiographically in the hemangiomatous soft
tissue masses. Lesions associated with both
Ollier’s disease and Maffucci’s syndrome carry a
significant risk of malignant degeneration.

23. Chondroblastoma
• It is less common than enchondroma.
• Chondroblastoma is composed of primitive cartilage cells, usually occurs in
the age group of 10 to 25 years.
• It is typically located in epiphysis and apophysis of bone, most often the
proximal humerus, distal femur and proximal tibia.
• On plain X-ray, chondroblastoma is an eccentric, lucent, well-defined lesion
with sclerotic borders. Periosteal reaction, far from the lesion is another
common feature suggesting an accompanying inflammatory process.
Approximately one-third of chondroblastoma have a calcified matrix which
can be better seen on CT scan.
• The tumor shows signal intensity similar to that of muscle on MR imaging;
however, the rim of the tumor has lower signal intensity. On T2 weighted
images, the signal intensity of the tumor is low to intermediate. This tumor
also shows extensive surrounding inflammation which may be confused with
more aggressive lesion. Malignant transformation of chondroblastoma is
extremely uncommon.
• The differential diagnosis of epiphyseal lesions includes giant cell tumor,
osteomyelitis, subchondral cyst.

25. Chondromyxoid Fibroma
• Chondromyxoid fibroma is rare and commonly
affects males and patients younger than 35
years.
• Histologically it is composed of chondroid,
myxoid and fibrous tissue in varying amounts.
• The common locations of tumor are ilium, tibia
and bones of foot.
• These tumors are located characteristically in
metadiaphyseal location unlike
chondroblastoma and do not cross an open
growth plate.

26. • On plain radiograph, it
appears as a well
marginated central or
eccentric lucent lesion,
with sclerotic margins
and cortical thinning.
Half of the lesions may
show parallel
orientation to the long
axis of the involved
bone. Matrix
calcification and
periosteal new bone
formation usually do
not occur.

27. FIBROUS TUMORS/LESIONS
Fibrous Cortical Defects and Nonossifying Fibroma
• Fibrous cortical defect and nonossifying fibroma are basically similar
benign fibrous lesions located slightly differently, nonossifying
fibroma being located eccentrically in the medullary cavity and
fibrous cortical defect seen superficially affecting the cortex.
• Pathologically, these lesions are composed of fibrous tissue,
xanthoma cells and giant cells.
• The common location of lesion are in the bones around the knee
joints.
• Asymptomatic and do not require specific treatment.
• On plain radiography, the lesion appears as well marginated
eccentric lytic lesion with scalloped margin. Its inner border is often
sclerotic and may appear multilocular due to corrugations.
• Differential diagnosis includes unicameral bone cyst, aneurysmal
bone cyst, fibrous dysplasia, and chondromyxoid fibroma.
• The signal intensity of nonossifying fibroma is equal to or less than
muscle on T1-weighted MR images and hypointense on T2-weighted
images. Postcontrast images usually show heterogeneous
enhancement.

30. Fibrous Dysplasia
• Fibrous dysplasia is disorders where bone is replaced by abnormal fibrous
tissue.
• Fibrous dysplasia can be monostotic, polyostotic.
• It is more common in young females.
• It is occasionally seen in the first decade of life.
• In a small percentage of cases (2–3%), fibrous dysplasia is associated with
endocrine disorders, especially precocious puberty in girls. Although it is not a
true neoplasm, fibrous dysplasia involving a long bone may mimic a bone
tumor or cyst. This type of fibrous dysplasia causes expansion of the medullary
cavity of tubular bones, endosteal scalloping and trabeculation. The margin is
sclerotic.
• The lesion may appear as ground glass or radiolucent, and this depends upon
amount of fibrous tissue within the lesion.
• Bowing of the affected long bone may occur; when the affected bone is femur,
the resulting deformity is called a “shepherd’s crook”. Thinning and
destruction of the bony cortex may be seen on CT or MR images. Soft typically
shows intermediate to low signal on fluid sensitive sequences.

33. Osteofibrous Dysplasia
• It is a rare lesion that is usually confined to the
tibia but can also involve the fibula.
• Most cases occur during the first decade of life.
On plain X-ray, the lesion appears as an eccentric,
lucent, solitary or multiloculated, lesion involving
the anterior aspect of tibia.
• CT is very helpful in determining its intracortical
location, an important feature in distinguishing
osteofibrous dysplasia from fibrous dysplasia.

34. VASCULAR AND CONNECTIVE TISSUE
TUMORS
Hemangioma
• Hemangioma is slowly growing lesions of bone composed of newly
formed vascular spaces.
• About 50 percent of hemangiomas of bone occur in vertebrae and are
most commonly located in lower thoracic and upper lumbar regions.
• Twenty percent of hemangiomas occur in skull. Small bones of the hand
and feet may also be affected.
• Hemangioma of the vertebra has a typical radiographic picture in the
form of coarse vertical striations on the plain radiographs and Polka dot
appearance on CT29.
• It shows high intensity on both T1W and T2W images. In the skull,
hemangioma generally affects the calvarium and is seen as an expansile
lytic lesion which has a sunburst appearance with striations radiating
from the center. In the short and long bones, the lesion lacks
characteristic features and may be difficult to differentiate from other
expansile central lesions such as aneurysmal bone cyst, chondromyxoid
fibroma or enchondroma.

36. OTHER TUMORS
Giant Cell Tumor
• Giant cell tumor (GCT) constitutes about 5 percent of all
bone tumors and slightly less than 20 percent of all
benign tumors.
• The tumor originates from undifferentiated cells of the
supporting tissues of bone marrow.
• As opposed to other benign tumors, GCT has a female
predilection and mostly occurs after the closure of
epiphysis, with a peak in the third decade.
• Giant cell tumors arise eccentrically in the metaphysis
with tendency to approach the adjacent subarticular
cortex as they enlarge.
• Forty to fifty percent of lesions occur around the knee.
Involvement of distal radius is seen in 10 to 12 percent
which otherwise is an uncommon site for bone tumors.

37. • Other sites are sacrum, short tubular bones and vertebral
bodies.
• Classical radiographic picture is that of a well defined
eccentric lytic lesion which expands the bone and is
usually not surrounded by a sclerotic rim.
• Cortical penetration with or without an associated soft
tissue mass is seen in 33 to 50 percent of cases.
• The solid portion of a giant cell tumor is usually low to
intermediate signal intensity at T1- and T2-weighted
images. This has been attributed to its high collagen
content, high cellularity or presence of hemosiderin.
• Giant cell tumor is the most common lesion associated
with secondary ABC. Following contrast administration,
there is diffuse enhancement of the solid component and
peripheral or septal enhancement of cystic areas.
• Giant cell tumors are aggressive benign neoplasms with a
high rate of recurrence.

39. TUMOR LIKE LESIONS
Simple Bone Cyst
• A bone cyst is a fluid filled lesion with fibrous lining.
• It occurs in metaphysis of long bones and adjacent to physis in children and
young adults.
• Common locations are proximal humerus and femur.
• Calcaneum and ileum are less common sites.
• On plain radiograph, the lesion appears as moderately expansile, well
marginated with or without sclerosis. The cortex may be thinned out and
may lead to pathological fracture.
• “Fallen fragment” sign has been described as pathognomonic features of
bone cyst when fragment of bone settles at the base of lesion due to simple
nature of fluid.
• “Rising bubbles” sign is also based on similar principles.
• CT and MRI can confirm the cystic nature of the lesion. The fluid contents
are usually of low intensity on T1-weighted images and hypertense on T2-
weighted images.3 However, hemorrhage into the cyst can alter the signal
characteristics of the lesion.

41. Aneurysmal Bone Cyst
• Aneurysmal bone cyst is solitary, expansile radiolucent lesion
and generally located in metaphysis of long bones.
• Other sites are dorsolumbar spine, small bones of hand, feet
and pelvis.
• Pathologically the lesion contains multiples cystic spaces
containing various stages of blood.
• Radiologically the lesion appears as expansile, lytic sharply
circumscribed with thin cortex.
• The characteristic features are its ballooned out appearance
and trabeculated appearance.
• CT may demonstrate fluid-fluid level and thin rim of bone
overlying the lesion.
• MRI shows the various stages of blood products which appear
as layers of different signal intensity on both T1 and T2W.
• The differential diagnosis includes giant cell tumor,
osteoblastoma, chondroblastoma, osteosarcoma and simple
bone cyst.