Aneurysmal bone cysts (ABCs) are benign but locally aggressive bone lesions consisting of widely dilated vascular channels that are not lined by an identifiable endothelium (23). ABC is usually diagnosed between ages of 10 and 20 years (24).

In Dahlin’s et al. (24) experience of 289 primary ABCs, only around 15% of the lesions affected the spine, usually arising from the posterior elements, often expanding to the pedicle and vertebral body.

The typical presentation is with persistent and progressive neck/back pain, at times associated with neurologic symptoms (4,25). On x-rays, the lesion presents with bone expansion, cortical thinning and disruption, mostly lytic with loculations, and “soap-bubble” appearance (26). MRI helps identifying the characteristic (but not pathognomonic) fluid-fluid levels and the relationship to the spinal cord and nerve roots (Fig. 35.1).

The treatment options range from selective arterial embolization to surgical resection. Biopsy is generally
recommended for definitive diagnosis. There are a few reports on the use of intralesional calcitonin and methylprednisolone (27). Percutaneous sclerotherapy has been used with good response (at least 80% decrease in size) in 16 of 17 patients in one series, after an average of two to five injections (28). Surgery is still the mainstay of treatment for large and symptomatic lesions. The use of adjuvants (e.g., phenol) is usually contraindicated due to the proximity to the spinal cord. Intralesional curettage and high-speed burring is done, followed by bone grafting. Spinal instrumentation may be needed depending on the extent of surgery. Local recurrence rates vary from 10% to 30% (4,25,26,29).

Osteoid osteoma and osteoblastoma are benign bone-forming lesions that have similar histologic characteristics but unique clinical and radiographic features. Osteoid osteoma is usually diagnosed in a slightly younger age group (5 to 24 years) than osteoblastoma (10 to 35 years). They frequently involve the spine (˜25% for osteoid osteoma and ˜40% for osteoblastoma), and the posterior elements are the usual site of involvement (5,8). In our experience with pediatric-only osteoblastomas, only one of five spine lesions involves the cervical spine (8). Pain is uniformly present, and among patients with osteoid osteoma, it tends to rapidly respond to aspirin or nonsteroidal anti-inflammatory drug (NSAID) medications (30). Scoliosis can be seen in up to 60% of the patients with spine lesions, especially in the thoracic area (7).

These lesions are difficult to visualize on plain radiographs, and CT is the best imaging method, superior to MRI (31). Lesions are classified based on their size, whereby lesions smaller than 1 cm are considered osteoid osteoma and lesions larger than 1.5 to 2 cm are considered osteoblastoma (5,32, 33 and 34). The lesion is usually well circumscribed and is characterized by a central nidus and abundant new bone formation (Fig. 35.2). Technetium bone scan is the most sensitive test for locating a spinal osteoid osteoma or osteoblastoma that cannot be easily visualized on x-rays.

Although osteoid osteoma may “burn out” with time, the symptoms can last for many years. Therefore, surgery is the preferred treatment for painful lesions refractory to conservative treatment or for progressive deformity. Excision does not require removal of the new bone formation/sclerotic reactive bone, although the entire tumor nidus must be removed. Depending on the location and size, the defect created by removal of the nidus is grafted. Spine instrumentation is sometimes needed for stabilization (titanium will allow for better postoperative imaging) (35). Pain relief after surgery is usually immediate, and the secondary scoliosis resolves in most cases. Recurrence rates after intralesional excision vary from 6% to 20% (8,24,36,37).

Eosinophilic granuloma is a benign and often self-limiting process that presents with focal bone destruction and subsequent repair (38,39). The etiology is still unknown, but lipid-containing histiocytes, numerous eosinophils,
and Langerhans cells comprise the lesion. Approximately 40% of the patients present with more than one site of involvement, and it is known as Langerhans cell histiocytosis (LCH) (40). It is more often in the first and second decades of life, and although it can be present in any bone, there is a slight predilection for the skull. In our series of 79 children with 165 lesions, there were 66 spine lesions, 27 (41%) of which involved the cervical spine (40).

Over 90% of children present with dull ache or pain at the lesion site; neurologic symptoms may be seen (40). With time, vertebral collapse may occur and produce muscle spasm and torticollis (40). The radiographic appearance varies; lesions may be solitary or multiple. Spinal lesions usually involve the anterior elements and can cause partial or complete collapse of the vertebral body, also known as “vertebra plana” (Fig. 35.3). Sometimes a flattened wedge of bone between the two intact adjacent intervertebral disks will have the “coin-on-edge” appearance. Spine lesions can be further classified based on the pattern of vertebral collapse. Skeletal survey is recommended to rule out multifocal disease.
Biopsy is usually needed for diagnosis confirmation since some malignant tumors, such as Ewing sarcoma, lymphoma, leukemia, and neuroblastoma may also present with vertebral collapse (41). The natural history of spinal LCH is such that isolated lesions tend to heal spontaneously, often with restoration of vertebral height (9,42, 43 and 44). Although several treatment options have been described from bed rest to bracing, steroid injection, and chemotherapy (9,38,42,45), our recommendation is to proceed with biopsy followed by a short period of bracing for pain control and perhaps prevention of vertebral collapse. Multiple lesions receive lowgrade chemotherapy. In cases where neurologic symptoms occur, excision of the tumor, followed by grafting and sometimes instrumentation, may be indicated (9,40).

Osteochondromas are one of the most common benign bone tumors (34). They are a tumor of “growth,” arising from the endochondral ossification of misplaced cells from the growing peripheral physis of the bone of skeletally immature children, appearing as a cartilage-capped bone exostosis (46). Vertebral involvement is unusual, occurring in less than 1% of the patients with solitary lesions but with a higher proportion among children with multiple lesions (multiple hereditary exostosis) (24,47).

Although osteochondromas are usually a painless mass, sometimes they grow and cause a mass effect with possible compression of adjacent structures such as spinal cord and nerve roots, causing pain and neurologic symptoms (48). In a review of 41 patients with solitary vertebral osteochondroma, the cervical spine was involved in 56% of the patients, most lesions arising from the posterior elements (48). Cervical cord compression and respiratory failure secondary to extrinsic osteochondroma compression of upper cervical spine have been reported (47).

On imaging, osteochondromas have characteristic appearance with a bony exostosis covered by a cartilage cap, and both the cortex and the medullary canal communicate with the medullary canal of the host bone (Fig. 35.4).
Biopsy is only necessary for rapid growing lesions, especially after skeletal maturity, or lesions without the typical radiographic appearance. The indications for surgical removal are painful lesions, neurovascular compromise, and suspected malignant transformation.

Ewing sarcoma is a malignant small round blue cell tumor of neuroectodermal origin. Approximately 95% of the tumors present with characteristic 11:22 chromosome translocation (5). Eighty percent of all patients are between the ages of 5 and 15 years (5,16,19,49). The most common areas of involvement include the femur, pelvis, and spine (19). Although Ewing sarcoma is the most common primary malignant bone tumor of the spine in children (49), spine lesions represent less than 10% of all osseous lesions (12,13,19) and are more often associated with metastatic disease. Lesions typically involve the vertebral body, and the cervical spine is the least common segment involved (5,13,19).

Pain is the most common complaint at presentation present in up to 97% of the patients (19). Pain can be localized, or radiated to the extremities, usually being present for several months prior to diagnosis. Tumor extension to the spinal canal is not unusual (14), and the majority of the patients have some motor or sensory dysfunction at the time of presentation. Bladder dysfunction is common with lower spine lesions (19). Constitutional symptoms, such as fever and malaise, may be present, especially in patients with metastatic disease.

Imaging exams reveal a lytic, mixed, or sclerotic lesion usually involving the anterior elements of the spine, sometimes with a vertebra plana appearance (50). Involvement of paraspinal soft tissue extension and extradural canal space invasion is best depicted on MRI.

Treatment includes neoadjuvant chemotherapy with subsequent local control by radiation, surgery, or both, and postoperative chemotherapy. Appropriate surgical local control by wide resection, when possible, provides a better long-term outcome when compared with radiation. The 5-year overall survival for spinal Ewing sarcoma varies from 33% to 48% (12,51). Metastasis at presentation and larger tumors are associated with poorer prognosis (<25% of survival at 5 years) (5,52).

Osteogenic sarcoma is the most common primary malignant bone tumor of children, representing 20% to 25% of all primary sarcomas of children, with 600 to 800 new cases per year in the United States (5,21,49). It usually affects children between the ages of 10 and 20 years, but it may occur at any age. There is a slight predominance in boys (1.3) over girls (53). Osteogenic sarcoma has been associated with multiple genetic aberrations and bizarre karyotypes. Losses of heterozygosity at the retinoblastoma (RB) gene locus on chromosome 13q and allelic loss or mutation in the region of the p53 gene on the short arm of the chromosome are frequent findings (54). History of RB increases the risk of developing osteogenic sarcoma by 2,000-fold (55).

Osteogenic sarcoma usually involves the metaphyseal ends of long bones (49,56). The incidence of axial skeleton involvement is around 10% and usually associated with poor prognosis (5). In a large series of 4,887 osteogenic sarcomas (adults and children), only 4% arouse primary in the spine. The majority of spine lesions involve the vertebral body (5,49). The thoracic spine and lumbar spine are the most common sites (14).

Pain is the most common symptom followed by local soft tissue swelling. Up to 70% of patients have neurologic abnormalities (18,57). Approximately 25% of the patients will have metastases at presentation, affecting the prognosis negatively (24).

Radiographs usually show a lytic or mixed blastic-lytic destructive lesion associated with soft tissue mass in 80% of the cases (53,57). CT scan is used for detection of pulmonary metastases and can also help delineating local bone destruction. The characteristic tumor pattern on MRI is disruption of the normal bone soft tissue architecture, low signal intensity on T1-weighted images, and high signal intensity on T2-weighted images.

The treatment consists of neoadjuvant chemotherapy followed by local control with surgery and postoperative chemo; radiation therapy is not effective. Surgery is usually deferred until the lesion has reduced in size or ossifies to enhance the likelihood of resection with appropriate wide margins. Survival for osteogenic sarcoma of the spine is poor, with 5-year rates between 3% and 10% (18).

Leukemia is the most common cancer of childhood (58). The peak incidence of leukemia is between 2 and 5 years of age, followed by a second peak from 15 to 20 years (11,49,59). Bone pain occurs as a result of leukemic cell proliferation in the medullary canal and under the periosteum, and it may be the presenting symptom in up to 25% of patients with acute lymphoblastic leukemia (5,11). Other commonly seen symptoms reflect a decreased production of blood cells and include pallor, lethargy, purpura, fever, hepatosplenomegaly, lymphadenopathy, and bleeding (5,49,58). Back pain and vertebral collapse is seen in 6% of patients (60).