Biopsy

In cases where the diagnosis is unknown, obtaining tissue for histologic diagnosis is the first step in the management of any spinal tumor. Biopsies must be planned with care as part of a comprehensive management strategy, to avoid tumor seeding along fascial planes or biopsy tracts; both increase risk of local recurrence. Areas of soft tissue extension or lytic destruction generally have the highest diagnostic yield. Some have suggested that resection of tissue along a biopsy tract can prevent recurrence cause by contamination of local tissues.

Biopsies can be separated into three categories: needle biopsy, open incisional biopsy, and open excisional biopsy. CT or fluoroscopic guided needle core biopsies allow for tissue diagnosis in up to 86% of cases and may be preferred over open biopsies given their lower morbidity profile. The major limitation of needle biopsies is inadequate tissue sampling, which can result in a nondiagnostic specimen, as is often the case with densely blastic lesions, necrotic tumors, or vascular lesions.

If an open biopsy is selected, the biopsy incision should allow for an eventual excision of the biopsy tract during future definitive surgical approaches. Meticulous hemostasis must be ensured, as hematomas can track along fascial planes with tumor cells in tow. Bony margins must be conservative so as to avoid introducing instability or pathologic fracture into a diseased spinal segment. Frozen section must be sent intraoperatively to confirm adequate tissue sampling. Culture should also be sent to rule out infectious pathology.

Medical Staging

The goals of surgical resection—oncologic cure, local control, or palliation—depend on the histology in question and, in the case of metastatic tumors, the burden of systemic disease. Tokuhashi and colleagues developed a preoperative scoring system for metastatic tumors to the spine based on general condition (Karnofsky score), number of extraspinal bone metastases, number of metastases in the vertebral body, presence of and resectability of metastases to the major internal organs, primary site of disease (more aggressive histology yielding higher scores), and presence of neurologic deficit (Frankel score) to predict patient prognosis and use said prognoses to guide general recommendations about the aggressiveness of treatment.

Tomita and associates also developed a scoring system to guide and more specifically characterize the degree of aggressive surgical resection, again using a prognostic scoring system. The Tokuhashi and Tomita scores, however, have yet to be validated, despite their widespread use, but are currently under investigation by the Global Spine Tumour Study Group. In the case of metastatic tumors of the spine, a variety of factors have been significantly associated with survival following spine surgery for specific histologies. Progressive systemic disease appears to be a negative prognostic factor preserved across multiple histologies and may recommend a more conservative treatment in certain patients.

No medical staging system has been popularized for primary spinal tumors, as they are rarely called for (though some primary spine tumors have been known to metastasize).

Surgical Staging and Classification

Enneking described a staging system initially used for tumors of the long bone that was subsequently applied to the primary tumors of the spine. The Enneking classification system helps to clarify goals of surgery and is a guide to adjuvant therapy. Both benign and malignant tumors can be classified using this system, and tumor grade is dictated by the local extent of disease and presence of metastasis.

Benign tumors are divided into three stages. Stage 1 refers to asymptomatic tumors surrounded by a true capsule; these tumors display and indolent growth pattern and rarely require surgery. Stage 2 refers to tumors growing actively that are symptomatic, surrounded by a thin true capsule, and adjacent pseudocapsule of reactive tissue; these tumors require intralesional or en bloc excision and recur infrequently. Stage 3 refers to tumors that are rapidly growing with only a thin or incomplete capsule surrounded by a hypervascular pseudocapsule; these tumors are locally aggressive and require en bloc resection with intent for wide excision.

Enneking’s system divides malignant tumors into three stages as well, with each stage further subdivided into type A lesions, where tumor remains within the confines of the vertebra, and type B lesions, where tumor extends beyond the vertebra into adjacent soft tissues. Stage 1 lesions are low-grade, slow growing, and surrounded by a thick pseudocapsule, which contains microscopic rests of tumor tissue. Stage 2 tumors are high-grade, rapidly growing lesions whose rapid growth precludes formation of a pseudocapsule and whose malignant growth pattern is characterized by recurrent seeding of the surrounding tissue with satellite nodules, skip metastases, pathologic fractures, and epidural extension. Stage 3 lesions are similar to Stage 2 tumors in their malignant growth pattern but are distinct in having metastasized to regional lymph nodes or distant organs.

Use of the Enneking system in the management of spinal tumors does, however, have some limitations, most of which center around the fact that the spine, unlike the appendicular skeleton, has critical adjacent structures that cannot be sacrificed without significant morbidity. The Enneking system does not account for the continuous nature of the epidural compartment, does not acknowledge the devastating implication of sacrificing the spinal cord and roots when wide local excision is recommended, and does not address the need to maintain spinal stability following aggressive oncologic resection.

The Weinstein-Boriani-Biagini (WBB) surgical staging system was designed to reflect the unique anatomic complexity of the spine and to dictate appropriate surgical approaches that spare the spinal cord without compromising surgical tumor margins. This system divides the vertebrae into 12 radiating zones, progressing in clockwise fashion from the spinous process (zone I) at 12 o’clock, as well as five concentric layers (A to E) in the transverse plane, with A representing extraosseous soft tissue, B superficial intraosseous, C deep intraosseous, D epidural tumor extension, and E intradural tumor spread. The cephalocaudal extent of the tumor is based on the number of spine segments involved. The system allows for a more reasonable approach to surgical planning by taking into account the underlying principle that en bloc excisions in the name of maximal oncologic resection must be balanced by the need to preserve the spinal cord and neurologic function. Depending on areas involved, the WBB system recommends anterior versus posterior approaches.

More recently, surgical scoring systems have been developed to aid in decision making for spinal metastasis. The Spinal Instability Neoplastic Score (SINS) has been developed to integrate considerations for surgical stabilization as a concern distinct from maximal oncologic resection. The scoring system uses tumor location, patient pain, bone lesion quality, presence of preoperative spinal deformity, degree of vertebral body involvement/collapse, and postero-lateral element involvement to classify lesions into three categories based on their composite score: stable, potentially unstable, or unstable. Potentially or definitively unstable lesions require instrumentation and fusion in addition to oncologic resection.

Medical Therapy

Chemotherapy, hormonal or immunologic therapy, steroid administration, embolization, and external orthosis may play a role in the management of spine tumors to a varying degree. In the case of metastatic tumors, chemotherapy is best suited to treat the primary and systemic disease, but it is poorly suited to relieve acute neurologic symptoms or spinal instability. In the case of primary tumors, chemotherapy has traditionally played little role in the treatment of spinal tumors. More advanced chemotherapy regimens and the development of new hormonal therapies and targeted therapies have showed great promise, however, in the medical treatment of traditionally chemotherapy-resistant primary and metastatic tumors.

Surgery

Unfortunately, the terminology used in describing different types of surgical resections can be confusing. Surgical strategies can generally be divided into en bloc or intralesional resections. Curettage and intralesional resection generally refer to piecemeal removal of a tumor, whereas en bloc resection, or spondylectomy, indicates the intended removal of the whole tumor in one piece, with a layer of intact, surrounding healthy tissue. The specimen is then submitted for histologic study to confirm the actual extent of resection, regardless of the surgeon’s intent. A specimen will be labeled “intralesional” when the surgeon has cut within the tumor mass, “marginal” if the surgeon has dissected along a reactive pseudocapsule surrounding the tumor but without preserving a margin of normal tissue, and “wide” if the plane of surgical dissection is surrounded by a rim of continuous healthy tissue (> 2 cm of healthy bone, reactive periosteum, or pleura). A wide resection is the intended goal of an en bloc procedure, but this goal is not always met. Intralesional resections provide symptom palliation but are less ideal from an oncologic perspective, resulting in a high incidence of local recurrence due to the presumed seeding of residual tumor cells into the resection cavity.

The goal of surgical management is dictated by the pathology in question and the patient’s symptomatology. In general, however, surgery may or may not provide tissue diagnosis and should decompress neural elements, achieve spinal stability, and, if possible, cure the patient. Instances of acute neurologic deficit, intractable pain, or progressive deformity usually require surgical intervention.

For metastases, surgical treatment is palliative in nature, reserved for intractable pain, acute neurologic deficit, or frank spinal instability . In the case of primary tumors, long-term local control, survival, and potential cure are generally dependent on en bloc tumor resection. Marginal en bloc resection with regional adjuvant may be curative for aneurysmal bone cysts, giant cell tumors, osteoid osteomas, and osteoblastomas, whereas chondrosarcoma, chordoma, Ewing sarcoma, and osteosarcoma require a true wide en bloc resection. Unfortunately, however, the extent of resection is often limited by the proximity of vital neural structures that cannot be sacrificed in an attempt to obtain surgical margins. However, some benign primary tumors do not require surgery. For example, hemangioma is often an incidental finding and surgery may not be appropriate unless clinical signs and symptoms are present. As always, patient age, general well-being, and expected morbidity from surgical procedures must be considered.

Complications

Despite the considered benefit of wide en bloc resection, such procedures require extensive surgical exposure and are associated with significant rates of morbidity and mortality. Bandiera and colleagues reviewed 134 consecutive attempted en bloc resections over a 17-year period and noted major complications in 43 cases with three deaths. Their analysis found that patients undergoing previous, failed resection at another institution were more likely to suffer major complications, though the complication rate in patients undergoing de novo surgical intervention was still 20%.

Radiotherapy

Radiotherapy has been used as an effective primary therapy for both primary and metastatic malignancies of the spine. Subsequent evidence supporting aggressive surgical resection and stabilization in instances of cord compression from metastatic disease has transformed radiotherapy into an adjuvant therapy in some instances, but external beam radiotherapy (EBRT) remains a staple of therapy in some cases without neurologic symptoms or instability or in cases of radiosensitive metastatic spine disease.

In the case of metastatic spinal tumors, EBRT is traditionally indicated for the primary treatment of radiosensitive metastatic spinal tumors, axial or radiculopathic pain in the absence of neurologic deficits, widespread metastatic disease not amenable to surgical resection, limited life expectancy, or medical comorbidities that preclude operative intervention.

In general, benign primary tumors (i.e., osteoid osteoma, osteoblastoma, osteochondroma) have poor response rates to EBRT. The development of postradiation sarcoma is a particular concern in this patient population. Other more aggressive primary tumors, such as osteosarcoma and Ewing sarcoma, may benefit from neoadjuvant chemotherapy followed by resection, but in general, these histologies as well as chondrosarcoma and chordoma are extremely resistant to radiation therapy.

Radiation therapy for primary tumors is particularly challenging, as the traditional radiation doses required to achieve local tumor control exceed radiation doses tolerable to the spinal cord. Experience with extremity sarcomas suggests that 60 Gy is required for postoperative radiation therapy to achieve good local control, whereas the spinal cord is thought to tolerate no more than 50 Gy when delivered in 200-CGy fractions.

Several therapies have been developed to address this shortcoming. Proton beam radiotherapy can deliver uniform dosing to the target volume (i.e., tumor) with a minimal dose to critical surrounding tissues (spinal cord, bowel, esophagus). These therapies have shown initial promise in the control of chordoma and chondrosarcoma, with reports of local control rate of 76% and 82%, respectively, in some series, though no clear superiority has been demonstrated over traditional EBRT. Proton beam therapy centers remain few, with only a handful of centers in the United States.

High-dose conformal photon therapy (three-dimensional conformal radiation therapy [3D-CRT]) is another technique using photon radiotherapy that allows for the delivery of cytotoxic doses to tumor volumes while minimizing risk of radiation-induced myelopathy. This process has evolved into the more advanced intensity-modulated radiation therapy (IMRT) that allows for delivery of inhomogeneous doses that are highly conformal to target tissues. Data have suggested that IMRT offers good local control with rates as high as 81% for primary malignancies and 75% for metastatic lesions.

More recently, spinal stereotactic radiosurgery (SSRS) has emerged as an important tool in the management of spinal neoplasms, particularly metastases, allowing for the delivery of higher conformal doses of radiation to smaller target volumes with decreased radiotoxicity to critical adjacent structures. SSRS has been shown to be effective in yielding pain relief and improving local control in the treatment of spinal metastases that were not causing significant neurologic deficits or structural instability. Although SSRS has revolutionized management of spinal metastases, even with stereotactic conformal dosing, the delivery of radiation doses to the epidural space is limited due to concerns for regional neurotoxicity. Insufficiently irradiated epidural metastatic disease may be a future source of recurrent disease and resultant neural element compression.

Benign Primary Tumors

Hemangioma

These benign lesions, which are rarely symptomatic, display a high prevalence in the general population, estimated at greater than 10% in autopsy studies. They typically occur in the fourth to sixth decades with slight female predominance and are usually found in the thoracic region (B29). They are most often found, incidentally, in the vertebral bodies during general workup for back or leg pain. Fewer than 5% of patients with hemangiomas develop symptoms. Hemangiomas often become symptomatic during pregnancy, in particular, as pathologic fractures, hematomas, or expansile vertebral body lesions. Surgery is typically reserved for lesions causing pathologic fractures or spinal cord and nerve root compression. Surgery is not indicated for pure axial pain and is generally reserved for cases presenting with nerve root or spinal cord compression. A review from the Mayo Clinic reported that only 2 of 59 patients required surgical decompression due to lesion progression and neural element impingement.

Imaging.

These lesions characteristically display coarsened trabeculae resembling a honeycomb pattern on radiographs, a “polka dot” appearance on CT, and a mottled, T1 isointense, T2 hyperintense, gadolinium-enhancing appearance on MRI. Angiography reveals contrast pooling within the lesion ( Fig. 109-1 ).

A, CT of a vertebral body demonstrating the typical trabeculated appearance of a hemangioma of the lumbar spine. B, T1-weighted sagittal MRI of the thoracic spine demonstrates an indeterminate mass, later pathologically proved to be a hemangioma involving the body and right pedicle of T2. This hemangioma displaced the thecal sac and produced mild to moderate deformity of the adjacent thoracic spinal cord. In asymptomatic patients, this appearance is often an incidental finding.

Histology.

Trabeculae are typically atrophic due to dysmorphic blood vessels, though occasionally they may be hypertrophic and sclerotic. Trabeculae may be fed by either cavernous or capillary vessels. Neural element compression may be seen from expansile growth within the vertebral body or an extension of soft tumor into the canal.

Management.

Surgical decompression is recommended for lesions causing pathologic fracture or neurologic deficit and decline. More traditional treatment algorithms using simple laminectomy followed by radiotherapy may be giving way to more aggressive, gross total resection supplemented by instrumentation and fusion. Traditional laminectomy followed by EBRT yielded a 93% rate of neurologic recovery without recurrent symptoms over a 52-month follow-up period, whereas laminectomy without radiotherapy resulted in tumor control rates of only 70% to 80%. Nevertheless, given to morbidity associated with radiotherapy, gross total resection should be endeavored if possible. Radiotherapy may be recommended as a stand-alone therapy for back pain or as an adjuvant to subtotal resection, whereas embolization is most commonly used as an surgical adjunct to reduce intraoperative bleeding. More recently, vertebroplasty and kyphoplasty have been advocated for treatment of symptomatic lesions, with excellent pain relief and little evidence of posttreatment instability reported.

Eosinophilic Granuloma

This spinal lesion presents as one manifestation of a spectrum of disease, which can range from an isolated, self-limited process—Langerhans cell histiocytosis—to a single component of a multi-system disease process—Hand-Schüller-Christian disease and Letterer-Siwe disease. Vertebral body involvement is seen in up to 17% of children with a male predominance (2–5 : 1), most commonly in the vertebral bodies of the thoracolumbar spine in young children (< 10). Eosinophilic granulomas involving the adult spine are rare, with only 13 cases of lumbar spine involvement reported. These lesions cause lytic destruction of the vertebral bodies secondary to local proliferation of histiocytes presenting as back pain, though pathologic fracture may result in deformity or direct neural element compression and deficit as well. Multilevel involvement is rare.

Imaging.

Radiographically, eosinophilic granulomas appear as well-demarcated, destructive bony lesions without apparent soft tissue mass. CT imaging classically will show a flattened vertebral body pancaked between well preserved intervertebral discs, a finding known as vertebral plana, with MRI revealing a T1 isointense, T2 hyperintense (“flare reaction”) image with soft tissue swelling, and avid enhancement following contrast administration. The preservation of adjacent disc spaces is useful in distinguishing this process from other differential considerations ( Fig. 109-2 ).

A 27-year-old man presents with a 2-month history of midback pain, leg weakness, and difficulty with urination. Examination showed him to be paraparetic 3/5 bilaterally with hyperactive reflexes. Axial ( A ) and sagittal ( B ) CT scans show a lytic process involving the T7 body and left pedicle and, to a lesser extent, T6. Sclerosis suggests an indolent process such as eosinophilic granuloma. C, MRI shows a soft tissue mass with destruction of the bone, extending into the canal and compressing the cord. There is extension of the soft tissue mass into the left paraspinal space. D and E, A left-sided transthoracic T6 partial and T7 total corpectomy was performed with humeral allograft, and screw and rod fixation. After 15 months, the patient continued to have back pain and some unsteadiness, although he had no leg weakness or sphincter complaints.

Management.

Conservative management is the primary course of action. Prior to any consideration of invasive therapy, biopsy is indicated. If diagnosis of eosinophilic granuloma is confirmed, in many cases, symptoms resolve spontaneously over time, with even restoration of vertebral body height in young children. Although observation is reasonable for asymptomatic lesions, bracing may be pursued in cases of a lesion-induced deformity that is not overtly unstable with appropriate activity restriction. Low-dose irradiation or corticosteroid injections are options in advance of surgery or in lesions or patients not amenable to open treatment. Chemotherapy is appropriate in cases of widespread systemic disease. Surgery is generally reserved only in cases of neural element compression or correction of progressive spinal deformity that has failed external orthosis. Generally, the disease regresses spontaneously with good prognosis and low recurrence rates.

Aneurysmal Bone Cyst

Aneurysmal bone cysts (ABCs) are benign, proliferative, non-neoplastic lesions that can occur in any part of the skeleton. The classic appearance and presentation of these cystic, blood-filled lesions should be familiar to any spine surgeon. They make up 1% to 6% of primary spinal neoplasms and commonly occur in the posterior elements of the thoracolumbar spine in patients between the first and third decade of life, with a slight female predilection. Primary ABCs are of unclear etiology, though a secondary form has been described in association with eosinophilic granulomas, simple bone cysts, osteosarcomas, chondroblastomas, or giant-cell tumors. The most common complaint is axial back pain at night, localizing to the site of the tumor, though neural element compression with myelopathy or radiculopathy, pathologic fracture, or spinal deformity may be noted. Clinical course progresses slowly over months, with rapid growth and progression rare but possible.

Imaging.

CT imaging will reveal a “soap bubble,” lytic, multilobulated lesion, whereas MRI reveals eggshell-thin bone containing fluid levels with variable T1 and T2 intensities consistent with blood of mixed chronicity and gadolinium enhancement. CT imaging is best suited to delineate the degree of bone destruction and full extent of the lesion, with MRI being helpful for identifying epidural extension and site of neural element compression ( Fig. 109-3 ).

Aneurysmal bone cyst (ABC). A, Plain radiograph of lumbar spine demonstrating the typical appearance of a lytic, eccentric, expansile lesion of the vertebral body and dorsal elements of L5, as observed with an ABC. B, CT of lumbar spine demonstrating the lytic lesion of the dorsal elements and the vertebral body, with the tumor having an osseous shell consisting of a thin rim of cortical bone surrounding the mass. C, Plain and subtracted angiographic views display the typical segmental vascular supply of an ABC with vascular staining.

Angiography will reveal blood filled cavities within the lesion. The angiography may have both diagnostic and therapeutic value.

Histology.

ABCs display septa containing fibroblasts and giant cells with reactive new bone intermixed. Mitotic activity is brisk, but no cytologic atypical is noted. Grossly, the lesions are lytic and expansile, extending to the cortex and violating the periosteum, often with associated hemorrhage. The lesions contain characteristic sinusoidal vessels with hypervascular stroma.

Management.

Spontaneous resolution of ABCs has been reported, thus incidentally discovered lesions may warrant an initial course of conservative management. Biopsy is rarely needed in the setting of characteristic radiographic appearance. If biopsy is required, open biopsy are preferred to allow for adequate control of hemorrhage and to provide adequate tissue sampling. Several nonsurgical treatment options exist. Percutaneous injection with fibrosing agents has been shown to successfully destroy symptomatic lesions with low recurrence rates, though concern for inadvertent migration of material in the vasculature and resultant embolization and stroke have been reported. Successful treatment with stand-alone arterial embolization has also been reported, with repeated rounds of embolization advocated in an effort to avoid open surgery.

Surgical excision is generally curative and may be coupled with preoperative embolization and low-dose radiation therapy. Given the destructive nature of ABCs the resultant instability caused, along with the frequent presence of neurologic deficits, complete surgical resection is often the treatment of choice. Intraoperatively, an eggshell-thin cyst of reactive subperiosteal bone is observed as the extent of the lesion, its removal often associated with brisk bleeding. The interior of the lesion is often soft, fleshy, and vascular with unclotted blood. With appropriate surgical excision, the recurrence rate low in most series. Subtotal excision, however, if associated with a high and rapid rate of recurrence, as is the case with simple curettage. Spinal instrumentation and fusion should be performed as necessary.

Osteoid Osteoma

These relatively common, benign tumors account for approximately 10% of primary spine tumors, have a male predominance (2–3 : 1), and occur in the second and third decade of life. Moreover, they account for 21% of surgically managed benign lesions. These lesions have a characteristic central nidus with interwoven bone and osteoid—when the nidus is less than 2 cm (although other authors have used 1.5 cm), the lesion is characterized as an osteoid osteoma, as opposed to osteoblastoma. The two tumor types are distinguished by size—tumors with a diameter > 2 cm are classified as osteoblastoma, tumors < 2 cm as osteoid osteoma. The distinction between the two is often unclear and they may represent a continuum.

These osteoblastic lesions typically occur in the posterior elements of the lumbar spine and are sharply demarcated from surrounding bone. Mechanical pain is the most common presenting complaint—in one series of 33 patients, all patients presented with pain exacerbated by exertion, with neurologic deficits rare, occurring in only 2 patients. Aspirin, traditionally, is remarkably effective as an analgesic. Less commonly, radiculopathy or myelopathy can result from neural compression. Osteoid osteoma is also a common cause of antalgic scoliosis in adolescents—surgery of the osteoid osteoma alone can be corrective if performed within 15 months of symptom onset or before the onset of a spinal curve, a point after which spontaneous correction may not occur.

Imaging.

CT imaging is the treatment of choice and reveals a destructive nidus surround by osseous, expansile sclerosis with scalloped margins. Technetium bone scans show intense, focal increase in activity on intermediate and delayed films. On MRI, the nidus is T1 intermediately intense, T2 hypointense, with nidal enhancement on gadolinium imaging. However, it is important to note that these lesions may be missed on MRI or plain radiography ( Fig. 109-4 ).

Giant-cell tumor in a 17-year-old girl with several years of low back pain and a 1-year history of leg weakness and urinary retention and constipation. A, The lateral plane film demonstrates a lytic lesion of S1, with erosion of the anterior cortex. B, The CT demonstrates the expansile intramedullary tumor with extension into the spinal canal. T1-weighted ( C ) and T2-weighted ( D ) MRIs reveal the bony tumor arising from S1 with extension anteriorly and posteriorly. E, One month following posterior decompression and stabilization, radiographs show satisfactory alignment with hardware in place. The patient later underwent anterior resections 5 and 26 months following the first operation. She is doing well, without recurrence, and received no radiation.

Histology.

Grossly, a rim of reactive bone usually surrounds the lesion. Microscopically, these tumors are characterized by connected, irregular trabeculae of woven bone with varying degrees of mineralization, with a loose, fibrovascular stroma.

Management.

Given the efficacy of nonsteroidal anti-inflammatory drugs (NSAIDs) at pain relief, conservative therapy is an option. However, long-term NSAID use is not without side effects and a subset of cases ultimately proved to be osteoblastoma. Therefore, surgery continues to be the definitive treatment if surgical morbidity is acceptable. With complete resection, immediate pain relief is seen in greater than 95% of cases. When only subtotal resection is possible, reoperation is recommended in the face of recurrence. Radiation does not play a role as a stand-alone or adjuvant therapy. In poor surgical candidates, radiofrequency ablation has been used with reported pain relief rates between 77% and 100%, complication rates between 5% and 24%, and recurrence rates between 5% and 12%.

Locally Aggressive (Benign) Tumors

Giant Cell Tumor

Giant cell tumor (GCT) is most frequently encountered in females during the third or fourth decade of life. These locally aggressive benign tumors constitute 4.2% of primary bone tumors, with approximately 6.5% of these occurring in the spine, half of those in the sacrum specifically. The most common presenting symptom is pain, localized to the site of the lesion, which may go unnoticed for months before the appropriate diagnosis is made—associated neurologic deficits are only occasionally noted—in a review of 24 patients with giant-cell tumor of the spine, pain was the presenting symptom in each patient, with half of those patients having some form of neurologic deficit. Malignant transformation is seen in approximately 10% of cases, with biologically aggressive lesions and high local recurrence rates after incomplete resection.

Imaging.

CT imaging demonstrates an expansile lytic, cystic lesion in the sacrum. MRI reveals a heterogenous, cystic appearing T1 and T2 hypointense lesion with areas of hemorrhage and gadolinium enhancement. An associated soft tissue mass can be seen if cortical margins are violated ( Fig. 109-5 ).

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