Spinal tumors consist of a large spectrum of various histologic entities. Primary
spinal tumors may arise from the spinal cord (intraaxial or intramedullary space),
the surrounding leptomeninges (intradural extramedullary space), or the extradural
soft tissues and bony structures (extradural space). Almost 60% of the spinal tumors
are located in the extradural space, whereas 40% are located within the dural sac.
Primary tumors of the spine are uncommon and represent < 5% of all bone neoplasms
as compared with secondary metastatic disease, multiple myeloma, and lymphoma.[1]
Clinical signs and symptoms of spinal tumors are variable and nonspecific. Most common
symptom is pain, which is present in 85% of patients with primary spinal tumors.[2] Other symptoms include back pain, weakness, radicular pain, and paresthesia, which
may often be attributed to degenerative disease. Together with the relatively low
incidence of spinal tumors in comparison with degenerative processes, a delayed diagnosis
is quite common.
Imaging features of the primary spinal lesions are often characteristic, and the various
available imaging modalities provide useful tools for narrowing the differential diagnosis
and for planning further clinical treatment ([Table 1]).
Table 1
Features of primary osseous spinal lesions
|
Age
Gender
% spinal involvement vs other anatomical locations
|
Location[a]
|
Characteristic features
|
MRI features[b]
|
Key facts
|
|
Enostosis
|
Any, M = F
|
Adjacent to endosteal surface of cortex
|
Spiculated margins,
Surrounding trabecular bone normal
|
*T1, *T2, no CE
|
No pain
Any bone may be involved
|
|
Osteoid osteoma
|
10–20 y, M/F = 2–3/1
10% in spine
|
Posterior elements (75%)
L > C > T > S
|
Radiolucent nidus < 2 cm, surrounding sclerosis/edema
|
*T1,**T2, diffuse, marked CE
|
Pain worsens at night and is relieved by salicylates
|
|
Osteoblastoma
|
10–30 y
M/F = 2–2.5: 1
30–40% in spine
|
Posterior elements (85%), extend to vertebral body
C > T = L = S
|
Expansile, lytic, multifocal mineralization, secondary ABC
|
*, **T1, *, **T2, diffuse variable CE
|
Pain is nonspecific
Osteolytic lesion > 2 cm with a sclerotic ring; may be aggressive
|
|
Aneurysmal
bone cyst
|
<20 y (%60)
F > M
12–30% in spine
|
Posterior element,
70–90% extend to vertebral body
T > L, C > S
|
Expansile, thin-walled cavities with fluid–fluid levels
|
**T1, **, ***T2,
*Peripheral, septal CE
|
Back pain is most severe at night; pathologic fractures may occur
|
|
Giant cell tumor
|
20–40 y (80%)
Rare before skeletal maturity
M/F = 1:2.5 in spine
7–15% in spine
|
Sacrum, vertebral body
|
Expansile, secondary ABC
|
**T1, *, **T2,
**Diffuse CE
|
|
|
Hemangioma
|
Any age
M = F
Aggressive type F > M
|
Vertebral body > posterior element
|
***T1, ***T2,
Fallows fat signal
**Diffuse CE
|
Well-circumscribed lesion with coarse vertical trabeculae
CT: white polka dots
|
May extend epidurally and cause vertebral fracture or cord compression
|
|
Osteochondroma
|
20–40 y
M/F = 3/1
< 5% spine
1–4% in solitary
7–9% in multiple form
|
Spinous transverse process > vertebral body
C (50%, predilection of C2) > T > L > S
|
Follows vertebral body
|
Sessile or pediculated, marrow continuity, cartilage cap
|
“Cauliflower” lesion; spinal cord compression is rare
|
|
Chordoma
|
30–60 y
M/F = 2:1
Sacral location: no gender predilection
|
Arising from notochordal remnants
Sacrococcygeal (50%) > sphenooccipital (35%) > vertebral body (15%)
|
*, **T1, ***T2 (higher than disk)
Septal, peripheral CE
|
Destructive midline mass with multiple septa, calcification, soft tissue mass
|
Histology: physaliphorous cells, distant metastases are uncommon, but secondary sites
may be involved
|
|
Chondrosarcoma
|
40–50 y
M/F = 2:1
3–12% spine
|
Thoracic spine
|
*T1, ***T2
***Septal, peripheral CE
|
Lytic, destructive mass with or without chondroid matrix (rings and arcs of calcification)
|
Malignant degeneration of osteochondroma or enchondroma is possible
|
|
Osteosarcoma
|
30 y
M/F = 1
0.6–3.2% spine and sacrum
|
Posterior elements 79%
Involving adjacent vertebra 17%
Spinal canal invasion 84%
|
*T1, *T2,
**Diffuse CE
|
Aggressive, permeative, destructive lesion-forming immature bone and soft tissue mass
|
May be associated with Paget disease and previous radiation therapy, high levels of
alkaline phosphatase, pulmonary metastases common, pneumothorax may occur
|
|
Ewing sarcoma/PNET
|
10–30 y
M/F = 2:1
3–10% spine
|
Sacrum > spine
Vertebral body + posterior elements
|
**T1, **, ***T2
**Diffuse CE
|
Permeative, lytic lesion with soft tissue mass
|
Localized pain; an elevated erythrocyte sedimentation rate may simulate osteomyelitis
|
|
Langerhans cell histiocytosis
|
< 20 y
6% in spine
|
Vertebral body
T > L, C
|
*, **T1, ***T2
**Diffuse CE
|
Vertebra plana
Intact end plates
|
|
ABC, aneurysmal bone cyst; CT, computed tomography; M/F, male-to-female ratio; MRI,
magnetic resonance imaging; PNET, primitive neuroectodermal tumor.
a C, cervical; T, thoracic; L, lumbar; S, sacral.
b *, low; **, intermediate; ***, marked; CE, contrast enhancement.
Benign Tumors of the Osseous Spine
Enostosis
Enostosis, also called a bone island, is a frequent benign hamartomatous osseous spinal
lesion with a developmental origin.[3] It is frequently located between T1 and T7 in the thoracic spine and between L2
and L3 in the lumbar spine. It is composed of cortical bone with irregular margins
merging with the medullary bone, commonly adjacent to the endosteal surface. The spiculated
or thornlike lesions are typically round or oval with a size up to 2 cm in diameter.
On magnetic resonance imaging (MRI) enostoses demonstrate low signal on both T1-weighted
images and T2-weighted images parallel to cortical bone. The surrounding trabecular
bone displays normal signal ([Fig. 1]). Intraosseous vacuum phenomena may mimic a focus of enostosis with low signal on
all sequences; however, it usually exhibits well-defined margins ([Fig. 2]). These features allow differentiation of these lesions from other sclerotic spine
lesions including osteoblastic metastases, osteoid osteoma, and low-grade osteosarcoma
in the vast majority of cases, avoid unnecessary evaluation, and obviate the need
for biopsy. However, biopsy may be considered if there is an increase in size. Enostosis
is a typically solitary lesion; however, multiple lesions are related to osteopoikilosis,
osteopathia striata, and melorheostosis.
Fig. 1 A sclerotic bone island in the upper half of the corpus of the C5 vertebra (arrows).
(a) T2-weighted sagittal, (b) T1-weighted sagittal images show a small lesion with low signal intensity, (c) lateral X-ray. The focus of enostosis with irregular margins has high density similar
to cortical bone.
Fig. 2 A 60-year-old female patient with intraosseous vacuum in the upper plate and body
of the L5 vertebrae mimicking an enostosis on magnetic resonance imaging (arrows).
(a) T1-weighted coronal, (b) short tau inversion recovery coronal images demonstrate a well-defined focus with
low signal. (c) Anteroposterior lumbar X-ray and (d) axial computed tomography image show the intraosseous air density with surrounding
sclerosis, related to adjacent degenerative disk disease.
Osteoid Osteoma
Osteoid osteoma is a benign bone tumor that occurs most frequently in young patients,
7 to 25 years of age, with a slight male predominance. Most patients experience pain
that worsens at night and is relieved by nonsteroidal anti-inflammatory drugs.[4]
[5] The pain may also be aggravated by the imbibing alcohol.
Osteoid osteomas are small (by definition < 2.0 cm in diameter) vascular lesions with
well-organized interconnected trabecular bone in a background of fibrous connective
tissue. These lesions are frequently surrounded by a variable degree of reactive bone
and are often associated with cortical thickening and bony sclerosis.
The lumbar spine is the most frequently affected portion of the spine (59% of lesions)
followed by the cervical (27%), thoracic (12%), and sacral segments (2%). Spinal osteoid
osteomas are located within the posterior elements of the vertebra (pedicles, superior
and inferior articular processes, lamina, transverse, and spinous processes) in 93%
of cases. The remaining lesions are located within the vertebral body.[6]
[7]
Osteoid osteomas are often difficult to detect on radiographs owing to their small
size, radiolucent appearance, and posterior element location. Computerized tomography
(CT) demonstrates a radiolucent nidus with or without intranidal calcification and
surrounding cortical thickening and sclerosis with great success ([Fig. 3]). More than 50% of nidi are partially calcified, ∼ 20% are completely calcified,
and 30% show no calcifications. However, some of these tumors may display misleading
imaging findings, making it difficult to differentiate these tumors from other diseases.
The central mineralization has a sequestrum-like appearance and may mimic osteomyelitis,
osteoblastic metastases, lymphoma, Langerhans cell histiocytosis (LCH), osteoblastoma,
and malignant fibrous histiocytoma. A vascular groove sign is a moderately sensitive
and highly specific sign for distinguishing osteoid osteoma from other radiolucent
bone lesions on CT.[8]
Fig. 3 Osteoid osteoma of the posterior elements of the D10 vertebra in an adolescent boy
with back pain worsening at nights. (a) Anteroposterior dorsolumbar X-ray shows very subtle sclerosis of the left peduncle
of the D10 vertebra in comparison with the right side, which is almost undetectable
(small arrowhead). (b, c) Axial computed tomography scan demonstrating the small radiolucent nidus (arrow)
at the base of the left transverse process as well as the surrounding sclerosis at
the peduncle, lamina, and transverse process (arrowheads). (d) T1-weighed axial and (e) T2-weighted axial magnetic resonance images showing edema pattern of the left transverse
process (arrowheads).
The nidus has low to intermediate signal on T1-weighted images and intermediate to
high signal on T2-weighted images on MRI. Surrounding reactive edema, both in the
marrow and soft tissues, can be extensive, may obscure visualization of the nidus,
and potentially suggest a more aggressive lesion. The soft tissue edema and delay
of diagnosis can lead to muscle atrophy in the chronic period. Although MRI has been
reported to be of limited value, dynamic contrast-enhanced MRI was found to show the
nidus more clearly in osteoma osteoid than nonenhanced MRI. Most osteoid osteomas
show arterial phase enhancement and rapid partial washout as a result of hypervascularity
of the nidus.[9]
[10]
[11]
Radiofrequency ablation is the preferred method for appendicular lesions and has been
used in the spine with some caution. Laser and alcohol ablation are also accepted
methods that may increase in use in the future.[12]
[13] Surgical excision is also curative if the nidus is completely removed.
Osteoblastoma
Osteoblastomas usually present in young adults between the second and third decades
of life. Men are affected twice as commonly as women. It is a rare benign osteoid-producing
tumor also called giant osteoid osteoma and osteogenic fibroma. Osteoblastomas commonly
affect the vertebral column (30–40% of cases) and most frequently originate from the
posterior elements (85% of lesions) with 42% extending into the vertebral body. They
may present with pain, paresthesias, paraparesis, or even paraplegia.[14]
Osteoblastoma and osteoid osteoma are variants of the same benign process and histologically
indistinguishable from each other. Only the size is used as a differential criterion
in which a lesion with a nidus > 2 cm is classified as osteoblastoma. The natural
history of osteoblastomas is slow growth as opposed to the relative stability of osteoid
osteomas. Malignant transformation to osteosarcoma is rare. Osteoblastomas are more
aggressive than osteoid osteomas, with a higher recurrence rate: 10 to 15% for the
less aggressive and > 50% for the more aggressive lesions.
Spinal osteoblastomas may present with variable radiologic appearances. First pattern
is similar to osteoid osteomas and composed of a radiolucent nidus and surrounding
sclerosis, but they are > 2 cm in diameter. The most common appearance of spinal osteoblastoma
is an expansile lesion with a prominent sclerotic rim and multiple small calcifications.
The more aggressive type demonstrates an expansile pattern with matrix calcifications,
bone destruction, and paravertebral extension mimicking an aneurysmal bone cyst or
bone metastasis ([Fig. 4]). Furthermore, aneurysmal bone cyst components are present in 10 to 15% of cases.[15]
Fig. 4 A 16-year-old male patient with chondroblastoma. (a) Sagittal T1-weighted, (b) sagittal T2-weighted, (c) axial gradient recalled echo T2*, (d) sagittal postcontrast T1-weighed, (e) axial postcontrast T1-weighted magnetic resonance images. A mass lesion of the C3
vertebra compressing on the cervical spinal cord with a cystic component at the body
(arrowheads) and a markedly enhancing mostly solid part involving the posterior elements
(arrows).
The diagnostic examination of choice is CT; however, MRI depicts the surrounding soft
tissue involvement to a better extent. CT shows the nidus, the multifocal (as opposed
to central in osteoid osteomas) matrix calcification, the sclerotic margin, the expansile
bone remodeling, or a thin osseous shell around its margins.
Surgical resection is the treatment of choice with a recurrence rate of 10 to 15%
for conventional osteoblastomas.[14]
[16] Rarely, aggressive osteoblastoma may undergo malignant transformation to osteosarcoma
and metastasize.
Aneurysmal Bone Cyst
Aneurysmal bone cyst (ABC) typically affects patients < 20 years of age, with a mild
female predilection. Overall, 12 to 30% of ABCs are located in spine. Thoracic spine
is the most frequently affected segment; lumbar and cervical involvement is less common.
Although very rare, sacral ABC is centered in upper segments, similar to giant cell
tumor (GCT). Spinal ABCs typically show marked expansile remodeling ([Fig. 5]). Although centered in the posterior elements, 75 to 90% of cases extent into the
vertebral body ([Fig. 6]).[17]
Fig. 5 Aneurysmal bone cyst at the body and left peduncle of the L3 vertebra. (a) Sagittal T2-weighted, (b) sagittal short tau inversion recovery, (c) axial fast spin-echo T2-weighted, (d) Sagittal T1-weighted, (e) postcontrast T1-weighted magnetic resonance images demonstrate a well-defined, slightly
expansile mass lesion with fluid–fluid levels (arrows) and minimal contrast enhancement.
Fig. 6 A 47-year-old female patient with neck pain with pathologic diagnosis of aneurysmal
bone cyst. (a) Anteroposterior X-ray lytic destructive lesion at the left side of C6–C7 vertebra
(arrows). (b, c) Fluid–fluid levels (arrowheads) demonstrated in the multilocular expansile lesion
involving both the body and posterior elements on consecutive computed tomography
images. Magnetic resonance imaging of the same patient. (d, e) Sagittal and (f, g) axial T2-weighted images demonstrate multiple fluid–fluid levels representing hemorrhagic
elements at various ages (arrowheads).
CT and MRI of a primary ABC show single or, more commonly, multiple fluid levels representing
hemorrhage with sedimentation.[18] During cross-sectional imaging, supine positioning for ∼ 10 minutes may be necessary
to detect fluid levels. MRI is also indispensable in determining the extent of the
lesion and the relationship to the central canal and nerve roots, like in all spinal
tumors. Methemoglobin within the fluid components show increased signal in both T1-weighted
and T2- weighted MR images ([Fig. 5]). A low signal intensity rim on all pulse sequences corresponds to an intact and
often thickened periosteal membrane. Thin rim-and-septal pattern of enhancement is
detected after contrast administration. The identification of fluid levels should
initiate a search for a solid component that enhances diffusely indicative of a primary
lesion (usually GCT or osteoblastoma) with secondary ABC.
The imaging findings closely resemble the histologic appearance of this tumor. Primary
ABCs have a characteristic appearance consisting of multiloculated blood-filled spaces.
These blood-filled spaces are not lined by endothelium and thus do not represent vascular
channels and are separated by thin septa. The septa interposed between the blood-filled
spaces are composed of fibrous tissue, giant cells, and reactive bone.[19]
The main surgical therapy for ABCs is curettage and bone grafting. The overall recurrence
rate for these lesions is 20 to 30% and may increase with incomplete resection.[20]
Giant Cell Tumor
Although commonly thought of as an appendicular lesion, 7 to 15% of GCTs can present
in the spine. Of the tumors located in the spine, the peak incidence is from the second
to third decades. These tumors are rare before skeletal maturity and usually present
in the second to fourth decade of life. The male-to-female ratio is 1:2.5. The sacrum
is the most commonly affected spinal location, followed by the thoracic, cervical,
and lumbar segments in descending order.[21]
[22] GCTs may increase rapidly in size during pregnancy, presumably due to hormonal stimulation.
GCT is a lytic, expansile lesion composed of osteoclast-like giant cells, with no
evidence of matrix mineralization. GCT of the sacrum, which is frequently centered
in the S1–S2 segment, may extend across the sacroiliac joint.[23] GCT usually affects the vertebral body with extension into the posterior elements
and paraspinal soft tissues. Vertebral collapse and involvement of the adjacent intervertebral
disks and vertebra may occur. A total of 90 to 95% of GCTs show low to intermediate
signal intensity on the T1-weighted and T2-weighted MR images.[24] Fluid–fluid levels on cross-sectional imaging representing secondary ABC components
should be avoided during biopsy because they do not harbor diagnostic tissue of the
primary tumor.
Osteochondroma
A cartilage-covered osseous excrescence in continuity with parent bone is an osteochondroma.
Hereditary multiple exostosis (HME), diaphyseal aclasis, hereditary deforming chondroplasia,
multiple osteochondromatosis, multiple cartilaginous exostosis, dyschondroplasia,
and Ehrenfried disease are alternative names.[25] Male-to-female ratio is 3:1. It is an uncommon tumor in the spine comprising only
1 to 4% of solitary exostoses and is usually discovered during the third and fourth
decades of life. In cases of HME, they present a decade earlier in 7 to 9% of patients.
Even if they can be located anywhere along the spine, they appear to have a predilection
for the cervical spine, particularly C2.[3] Because lesions protruding into the spinal canal lead to neurologic symptoms earlier,
they are often discovered when they are smaller, in comparison with lesions projecting
posteriorly.[26]
Osteochondromas of the spine are often difficult to detect on radiographs because
of the complex osseous anatomy and frequent small size of lesions. The continuity
of the marrow and cortical portions of the bone from which it originates is pathognomonic
and best evaluated with thin-section multiplanar CT images ([Fig. 7]). The hyaline cartilage cap (low to intermediate signal on T1-weighted and high
signal intensity on T2-weighted MR images) is usually apparent with MRI. A cartilage
cap thicker than 1.5 cm in adults is suspicious for malignant transformation to a
chondrosarcoma. Surgical excision with resection at the point of cortical and marrow
junction to the underlying bone is usually curative.
Fig. 7 Two different patients with osteochondromas of the spine. First patient: A 45-year-old
man with a osteochondroma originating from the right C5–C6 facet joint. (a) Anteroposterior (AP) cervical X-ray, (b) axial computed tomography (CT) scan demonstrates a well-defined bone-forming tumor
with lobulated contours (arrowheads). Second patient: A 36-year-old woman with back
pain. (c, d) AP and lateral X-rays, (e, f) axial CT scan shows similar imaging findings at the right superior articular process
of L2 vertebra (arrows).
Hemangioma
Hemangiomas are common, usually incidentally discovered benign developmental lesions.
Reported incidence in autopsy series is 11% of spines, and multifocal lesions are
present in 25 to 30% of cases.[27] Lesions occur most frequently in the thoracic spine but may be present at any spinal
level.[28] Hemangiomas reveal prominent vertical trabeculae on radiographs resembling a “honeycomb”
and classically called the “corduroy sign.” They form the appearance of multiple punctate
areas of sclerosis on axial CT images, creating the “white polka-dot” sign. Fatty
stroma and serpentine vascular channels are responsible for the low density components
on plain radiographs and CT images. The fat overgrowth exhibits signal parallel to
subcutaneous adipose tissue, and the vascular components demonstrate high signal intensity
in a serpentine pattern on T2-weighted MR imaging reflecting slow blood flow. The
polka-dot or corduroy appearance may also be seen, respectively, on axial and sagittal/coronal
MR images as low signal intensity regions ([Fig. 8]).
Fig. 8 (a) Axial computed tomography (CT) scan image showing multiple punctate areas of sclerosis
creating the white polka-dot sign. (b) Coronal and (c) sagittal reconstructed CT images displaying prominent vertical trabecula of corpus
of the D12 vertebra resembling a honeycomb and forming the “corduroy” sign. (d) Sagittal T1-weighted and (e) sagittal T2-weighted magnetic resonance images demonstrating two hemangiomas at
the D12 and L1 vertebrae with high signal intensity (arrows).
Histologically, hemangiomas represent a collection of thin-walled endothelial-lined
blood vessels interspersed between nonvascular components, such as fat, muscle, fibrous
tissue, or bone. Multiple types (capillary, cavernous, arteriovenous, and venous)
have been described, with the capillary type the most common.[29]
Hemangiomas with extension into the posterior elements, with paraspinal involvement
and without a large amount of intertrabecular fatty stroma, are more likely to be
associated with symptoms. Lesions containing less fat and more vascular stroma tend
to be less common, and they are located between T3 and T9. Large hemangiomas that
weaken the vertebral bodies can result in fractures. Pathologic fracture or epidural
extension may show a characteristic “curtain sign.” A vertebral body lesion extending
posteriorly to the anterior epidural space displaces the posterior longitudinal ligament.
However, this displacement is limited by the strong medial fixation, giving a bilobular
aspect to the epidural mass in the axial images, which is commonly called “curtain
sign.” Current treatment options for symptomatic vertebral hemangiomas include endovascular
embolization, vertebrectomy, sclerotherapy, and vertebroplasty.[30]
Langerhans Cell Histiocytosis
Langerhans cell histiocytosis (LCH) is a benign lesion that can affect the spine in
6% of cases. The thoracic segments are more commonly affected than the lumbar and
cervical regions.[31]
Radiologically, LCH demonstrates focal lytic lesions that may progress to uniform
vertebral collapse forming the classic appearance of “vertebra plana,” which is seen
in only ∼ 15% of cases. The end plates are typically preserved. Partial vertebral
collapse and focal marrow replacement may also occur.
The MRI appearance of LCH reveals areas of low signal marrow replacement on T1-weighted
and high signal intensity on T2-weighted MR images ([Fig. 9]). Findings may be very subtle on plain films ([Fig. 10]). MR imaging may also depict the soft tissue component ([Fig. 11]). Small areas of soft tissue extension and surrounding hematoma secondary to vertebral
collapse may be detected. MR imaging is useful in discriminating active disease from
chronic changes, which are seen as vertebral body deformity without abnormal signal
intensity. LCH can be self-limiting if involvement is restricted to bone and may not
require active treatment,[31] but close observation is necessary to exclude progression of disease. Therapeutic
options include low-dose radiotherapy, steroid injections, chemotherapy, and surgical
curettage.[32]
Fig. 9 A 22-year-old woman with Langerhans cell histiocytosis. (a) Lateral X-ray of the dorsolumbar spine demonstrating vertebral collapse more prominent
on the ventral side with preservation of the end plates. (b) Sagittal T2-weighted magnetic resonance (MR) image demonstrating vertebra plana
with slightly high T2 signal and small soft tissue component under the anterior longitudinal
ligament. (c) Sagittal T1-weighted MR image shows anterior compression at the D12 vertebral body
with low T1 signal. (d) Sagittal postcontrast T1-weighted MR image with fat saturation shows marked enhancement
of the pathologic compression fracture (arrows).
Fig. 10 A 22-year-old patient with Langerhans cell histiocytosis. (a) Lateral lumbosacral X-ray, (b, c) axial computed tomography images display small lytic lesion on the anterior aspect
of the S1 vertebra (arrows). A small focus of destruction accompanies at the dorsal
side of left sacral wing (arrowhead).
Fig. 11 Magnetic resonance (MR) examination of the same case. (a) Sagittal short tau inversion recovery image. (b) Sagittal T1-weighted, (c) axial T1-weighted MR images, (d) fast spin-echo proton density axial MR image with fat saturation, (e) postcontrast T1-weighted MR image with fat saturation demonstrates pathologic bone
marrow signal with a small soft tissue component and cortical destruction (arrows).
Malignant Tumors of the Osseous Spine
Chordoma
A chordoma is a malignant tumor arising from the embryonic remnants of the notochord
that extend from Rathke pouch to the coccyx. Histologic identification of physaliphorous
(“bubble bearing” vacuolated) cells confirms the diagnosis. It is the most common
nonlymphoproliferative primary malignant neoplasm of the spine in adults.
It commonly presents in middle-age patients and has a peak incidence in the fifth
decade and rarely detected before 30 years of age. Chordomas are almost exclusively
seen in the midline. Approximately 50% of chordomas are localized to the sacrum and
35% localized to the clivus. Unlike GCT, which prefers the upper sacral segments,
sacral chordomas are most frequently centered in the lower sacrum (S3–S4). The remaining
15% of chordomas affect the mobile spinal segments, particularly the cervical region.
It is very rare for chordomas to arise in a paracentral location, which is along the
spine in the soft tissues and in this case they are called “parachordoma.”[33]
[34]
Bone destruction predominates in spinal chordomas, although lesions affecting the
mobile portions of the spine may show sclerosis. A total of 64% of sacrococcygeal
lesions show intratumoral calcification[35] ([Fig. 12]). Chordomas originating in the spine almost invariably extend into the paraspinal
soft tissues, and the sacroiliac joint is crossed in 23% of cases.[33] Chordomas show signal characteristics parallel to nucleus pulposus of the disk (notochord)
in MR imaging, that is low-intermediate signal on T1-weighted and very high signal
on T2-weighted MR images ([Fig. 13]). However, spheno-occipital and intracranial chordomas may display high signal on
T1-weighted images due to high protein content.[34] Contrast enhancement is usually in a thick peripheral and septal pattern similar
but more prominent than chondrosarcoma ([Fig. 14]). The location and thus resectability of the lesion usually determines the patient's
prognosis. Local recurrence is common; distant metastases are rarer.
Fig. 12 A 59-year-old man with sacral chordoma. (a, b) Axial computed tomography scan and (c) coronal reconstructed images show lytic destructive sacral mass lesion with intratumoral
calcification.
Fig. 13 Magnetic resonance (MR) examination of the same patient with sacral chordoma. (a) Sagittal T2-weighted, (b) sagittal T1-weighted, (c) sagittal short tau inversion recovery MR images. Lobulated mass lesion with heterogeneous
signal characteristics originating from the lower sacral segments has a large soft
tissue component extending into the pelvis, epidural space, posterior elements, and
paravertebral muscles.
Fig. 14 Postcontrast (a) sagittal and (b, c) axial T1-weighted magnetic resonance images of the same patient show mild enhancement
of the mass lesion, abutting but not crossing the sacroiliac joints.
Chondrosarcoma
A malignant tumor of connective tissue, chondrosarcoma is characterized by formation
of chondroid matrix by tumor cells. It is the second most common nonlymphoproliferative
primary malignant tumor of the spine in adults. The spine represents the primary site
in 3 to 12% of chondrosarcomas.[36] The male-to-female ratio is 2–4:1, and the mean age of presentation is 45 years.
Although chondrosarcomas can be located at any level, the thoracic segments of the
spine are the more commonly affected ([Fig. 15]).
Fig. 15 A 47-year-old man. (a) Posteroanterior and (b) lateral chest X-ray demonstrating right paravertebral mass lesion with curvilinear
calcifications at the lower thoracic level.
These tumors can present as primary chondrosarcomas or as malignant transformation
of osteochondromas or enchondromas. Most spinal chondrosarcomas are histologically
low-grade lesions. They may be centered in the vertebral body or posterior elements
with destruction of the osseous structures and frequent involvement of the posterior
elements (40%). Mineralized chondroid matrix with typical ring-and-arc-nodules pattern
is best appreciated on radiographs or CT image ([Fig. 16]).[36] On MR imaging the nonmineralized lobular areas of hyaline cartilage growth typically
demonstrates low signal intensity on T1-weighted images and high signal intensity
on T2-weighted images ([Fig. 17]) and frequently reveal a peripheral and septal enhancement pattern on postcontrast
images ([Fig. 18]).
Fig. 16 Computed tomography (CT) examination of the same patient. (a) Coronal, (b, c) sagittal reformatted, (d, e) axial CT images demonstrates the calcified right paravertebral mass lesion displacing
the liver and right kidney. The adjacent posterior rib is sclerotic.
Fig. 17 Magnetic resonance (MR) imaging of the same patient. (a) Axial and (b) sagittal T1-weighted, (c) axial fast spin-echo T2-weighted with fat saturation, (d) sagittal short tau inversion recovery, (e, f) axial in-phase and out-of-phase MR images of the right paravertebral mass lesion
displaying a chondroid matrix with low T1 and high T2 signal intensity.
Fig. 18 Magnetic resonance (MR) imaging of the same patient. (a) Axial, (b) sagittal, (c) coronal postcontrast T1-weighted MR images with fat saturation showing septal and
peripheral enhancement of the mass lesion.
Treatment for spinal chondrosarcoma is surgical resection when possible. Incomplete
resection frequently leads to recurrence and eventual patient demise in 74% of cases.[36]
Osteosarcoma
An osteosarcoma is a malignant tumor containing immature matrix and osteoid produced
directly by the neoplastic cells. It is also called an osteogenic sarcoma. Overall,
0.6 to 3.2% of osteosarcomas occur in the spine. Spinal localization has a peak incidence
in the fourth decade, which is higher than the appendicular osteosarcomas; the age
range is 8 to 80 years.[36]
[37]
[38]
There is a male predilection. The patients present with pain, palpable mass, neurologic
symptoms, and high serum alkaline phosphatase levels. Pulmonary, bone, and liver metastases
are common. Osteosarcoma may be associated with Paget disease and previous radiation
therapy. It may also present as a second tumor ∼ 10 years after detection of retinoblastoma.[39]
Although they have been reported at all levels of the spine, a predilection for the
thoracolumbar segments is present. Spinal osteosarcomas tend to be high-grade lesions
that are predominantly osteosclerotic. The heterogeneous mass with ossified and nonossified
components is commonly associated with necrosis displaying a mixed osteosclerotic-osteolytic
appearance on conventional radiographs and CT images ([Fig. 19]). An ivory vertebral body may be recognized with loss of vertebral height, permeative
or moth-eaten pattern of bone destruction, cortical interruption, a wide zone of transition,
and accompanying soft tissue mass. MRI is useful for evaluating extension of the lesion,
particularly the soft tissue component and involvement of the surrounding nerve roots
and spinal canal. Mineralized component of the tumor shows low signal in T1-weighted
and T2-weighted MR images; the nonmineralized portion of the tumor displays high signal
on T2-weighted sequences ([Figs. 20] and [21]). In telangiectatic osteosarcoma, a soft tissue mass and fluid–fluid levels are
typical. Osteosarcomas display heterogeneous contrast enhancement fallowing contrast
administration.
Fig. 19 (a–c) Axial computed tomography scans. (d) Sagittal, (e) coronal maximum-intensity projection reformatted images of a 19-year-old teenager
demonstrating a bone-forming tumor infiltrating the corpus and left wing of the sacrum.
Fig. 20 Magnetic resonance (MR) imaging scan of the same patient 6 weeks after open biopsy
and palliative radiation therapy. (a) Sagittal T1-weighted, (b, c) axial T1-weighted, (d) sagittal postcontrast T1-weighted MR image with fat saturation. Destructive mass
lesion of the sacrum invading the L5 vertebra and sacroiliac joints with accompanying
presacral and epidural soft tissue component. Note the fatty bone marrow infiltration
due to radiation therapy (white asterisks).
Fig. 21 Same patient following adjuvant chemotherapy with partial response. (a) Sagittal T2-weighted, (b) T1-weighted, (c) postcontrast T1-weighted magnetic resonance images with fat saturation.
As with Ewing sarcoma/primitive neuroectodermal tumor (PNET) lesions of the spine,
complete surgical resection with spinal osteosarcomas is usually not possible. Death
usually occurs within 1 year of diagnosis. The survival rates are lower in patients
with sacral tumors.[36]
Ewing Sarcoma and Primitive Neuroectodermal Tumor
Ewing sarcoma and PNET are indistinct entities with very similar pathologic, clinical,
and radiologic characteristics. They are the most common nonlymphoproliferative primary
malignant tumors of the spine in children and adolescents. There is mild male predilection.
Lesions of the spine account for 3 to 10% of all primary sites of Ewing sarcoma/PNET.[36]
[40] However, metastatic involvement of spine from other foci of primary Ewing sarcoma/PNET
is much more common than primary lesions. The most common location for primary lesions
is the sacrococcygeal region, followed by the lumbar and the thoracic spine. Cervical
spine involvement is rare.[40]
Histologically, they are composed of small round blue cells with large irregular sheets
of cells divided by septa, scant cytoplasm, and abundant collagen. Spinal lesions
frequently display areas of necrosis.[41] These tumors have various radiologic patterns with most demonstrating aggressive
bone destruction, lysis, and large paraspinal soft tissue components. Vertebra plana
has also been reported. MR imaging shows intermediate signal intensity on T1-weighted
and intermediate to high signal intensity on T2-weighted MR images ([Fig. 22]).
Fig. 22 A 21-year-old male patient with a lumbar Ewing tumor. (a) Coronal T1-weighted, (b) sagittal T1-weighted magnetic resonance images, (c) short tau inversion recovery image, (d) axial fast spin-echo proton density with fat saturation image shows a mass lesion
at the right side of the L3 vertebral body (arrows) with a small soft tissue component
infiltrating the left psoas muscle (arrowheads).
Similar to osteosarcomas of the spine, surgical resection is often not feasible because
of the lesion location and large size of soft tissue components. Chemotherapy and
radiation treatment are the mainstay of therapeutic options.
