Primary Malignant and Benign Tumors of the Spine

Overview

Spinal tumors are generally categorized by location, and they fall into three anatomic groups: 1) extradural, 2) intradural-extramedullary, and 3) intramedullary. Primary malignant and benign tumors are typically extradural lesions. Compared with metastatic lesions of the spine, these tumors are rare and comprise less than 10% of spinal column tumors ( Table 64-1 ). These tumors may be found in both pediatric patients and adults. The initial age at presentation correlates to the aggressiveness of the tumor: the older the patient, the more likely the lesion is to be malignant (mean age at diagnosis is 21 years for a benign lesion and 49 years for a malignant lesion). In patients older than 21 years who are diagnosed with primary spinal tumors, 70% of the lesions are identified as malignant. Therefore primary tumors diagnosed in patients over the age of 30 should be considered malignant until proven otherwise.

Table 64-1

Common Primary Malignant and Benign Spinal Tumors Organized in Order of Incidence

PRIMARY MALIGNANT TUMORS

Multiple myeloma/plasmacytoma (most common)
Ewing sarcoma (most common in pediatrics)
Chondrosarcoma
Osteosarcoma
Chordoma *

PRIMARY BENIGN TUMORS

Hemangioma (most common)
Osteoid osteoma/osteoblastoma
Giant cell tumor *
Chondroma/enchondroma/osteochondroma
Aneurysmal bone cyst

* Locally aggressive

Presentation

Primary tumors of the spine often have a variety of subtle and nonspecific symptoms because of to the insidious nature of the disease. However, pain is present in nearly 85% of patients on initial evaluation. The hallmarks of destructive lesions of the vertebral column, both primary and secondary metastatic lesions, are nocturnal pain and pain related to recumbency. A high index of suspicion must be maintained for patients with non–weight-dependent pain. Pain, as well as neurologic symptoms that include weakness and bowel and/or bladder dysfunction, may result from pathologic fracture, tumor vascular engorgement, or periosteal stretching leading to neural compromise. Rarely, patients present with point tenderness over a particular dermatomal segment that can aid in diagnosis. On physical exam, 55% of the patients with malignancy and 35% with benign primary spinal lesions will have neurologic deficits. Occasionally, a palpable mass or spinal deformity may be identified.

Evaluation

Clinicians should have a higher suspicion for neoplastic etiology when patients come to medical attention with nocturnal pain, pain at rest that has persisted for more than 3 months, or progressive neurologic deficits; any of these should prompt an initial radiographic evaluation. Plain radiographs of the appropriate location, both anteroposterior (AP) and lateral views, can help identify the spinal lesion. However, 30% to 50% of the vertebral trabeculated bone must be resorbed before a lytic lesion can be detected. Computed tomography (CT) and magnetic resonance imaging (MRI), both with and without contrast, can be used to help identify the exact location, characteristics, and extension of the lesion. CT reveals the extent of the bony destruction, and MRI identifies the soft tissue and neural involvement. Other imaging techniques—such as arteriography, bone scan, CT myelography, and positron emission tomography (PET)—may help better characterize the tumor and distant metastatic lesions. Laboratory studies should include complete blood count, comprehensive metabolic panel, and urinalysis.

To rule out more common metastatic pathology, initial evaluation should consist of a CT scan of the chest, abdomen, and pelvis with and without contrast; nuclear scans; and MRI of the neural axis (brain through sacrum). Laboratory tests should include serum calcium levels, prostate-specific antigen, alkaline phosphatase, carcinoembryonic antigen, and serum and urine protein electrophoresis.

Management

The presenting neurologic deficits and the nature of the lesion as revealed by imaging studies play an integral role in determining the management of the spinal tumor. A biopsy of the lesion must be performed prior to attempting resection ( Fig. 64-1 ). When a lesion is found posteriorly, excisional biopsy may be considered, but the default should be an incisional or needle biopsy for presurgical diagnosis. For the thoracic or lumbar spine, a transpedicular needle biopsy with fluoroscopy or CT provides accuracy over 95% and has a complication rate of 0.2% to 0.7%.

An interdisciplinary approach should be adopted and must include the oncologist, radiation specialist, interventional radiologist, pathologist, and spinal surgeon for the appropriate management of these tumors. The location, histology, and presenting clinical features of the lesion determine the surgical and other nonsurgical modalities used for treatment. More importantly, the wishes of patients and their families should also be respected, and their expectations should coincide with those of the physician.

With progressive neurologic deficits, early surgical intervention should be considered, and the need for instrumentation should be anticipated if there is significant bony destruction, or if significant bone resection is required that may lead to iatrogenic instability. The goal of surgery varies with the specifics of the tumor pathology and the stage of the lesion (e.g., metastatic lesions). Preoperative endovascular embolization of the lesion may assist with the resection by limiting blood loss, especially in highly vascular lesions, such as renal cell carcinoma. Radiotherapy and chemotherapy may also play a role in both preoperative and postoperative management.

To develop the optimal treatment regimen for a particular lesion, the understanding of the anatomic and cytologic characteristics and subtleties of these tumors is necessary. Numbers of scoring systems have been developed to assist with surgical decision making and related prognosis and complications. These include Harrington classification, Modified Bauer score, Tomita scoring system, modified Tokuhashi scoring system, Van der Linden score, Spine Instability Neoplastic Scoring (SINS) system, and the “LMNOP” system (see Chapter 65 , Table 65-2 , Table 65-3 , Table 65-4 , Table 65-5 , for modified Tokuhashi, Tomita, SINS, and LMNOP systems). Sioutos et al identified the preoperative neurological status, anatomic site for primary carcinoma, and number of vertebral bodies involved as poor prognostic indicators, and radical resection is not recommended for patients with spinal metastases and cord compression if two or more of these factors are present.

To anticipate the utility of an en bloc resection of spinal lesions, many surgeons describe the tumor using the Weinstein-Boriani-Biagini (WBB) staging system ( Fig. 64-2 ). Prior to WBB surgical staging, the final tumor diagnosis must be known. The WWB system divides the vertebrae and adjacent soft tissue into twelve zones and five concentric layers. This allows the surgeon to determine the approach or combination of approaches for the en bloc resection: vertebrectomy comprises zones 4 through 8 and 5 through 9; sagittal resection, zones 3 through 5 and 8 through 10; or resection of the posterior arch based on the zones, specifically, zones 3 through 10, counterclockwise. This also allows the surgeon to anticipate which lesions may not be amenable to complete en bloc resection. Weinstein and colleagues believe that determination of the tumor location in the wedge sectors helps preserve vital structures and maximize the tumor resection with appropriate margins.

Malignant Tumors

Multiple Myeloma and Plasmacytoma

Plasmacytoma and multiple myeloma are the most common primary malignant tumors of the vertebral column. Kelley and colleagues reported a 42-year survey from a tumor registry that noted that 26% of primary vertebral tumors were plasmacytoma or multiple myeloma. Plasmacytoma is a solitary lesion limited to one or two foci, whereas multiple myeloma is a more systemic disease. Both are B-cell lymphoproliferative diseases with a male/female 2 : 1 predominance and a peak age of 55 years old. These lesions have a propensity for the posterior elements of the vertebral body and are most commonly found in the thoracic spine.

Initial evaluation should include diagnostic radiography, CT, and MRI of the spinal axis. Plain radiographs illustrate the degree of osteolysis or “punched out” radiolucent areas. CT and MRI will help determine bony destruction and soft-tissue compression of the neural elements, respectively ( Fig. 64-3 ). Serum and urine immunoelectrophoresis may show abnormal Bence-Jones proteins, which will aid in the diagnosis of the disease.

When neural compromise or spinal instability is evident, surgical intervention may include decompression and/or instrumentation. Vertebroplasty and kyphoplasty are reserved for pathologic compression fractures with intractable pain, without neurologic compression, and with competence of the posterior vertebral body, to prevent cement extravasation. However, radiation and medication are the initial treatment of choice. In myeloma patients, increased osteoclastic activity and inhibition of osteoblasts results in increased bone resorption and decreased bone formation. Bisphosphonates, such as pamidronate or zoledronic acid, are currently the standard of care to inhibit bone resorption. However, bone anabolic agents such as bortezomib may be used as therapeutic agents to target osteoblasts, reduce tumor burden, and improve bone health. Chemotherapy and bone marrow transplantation are used for more systemic disease.

Solitary plasmacytoma has a 5-year disease-free survival of approximately 60% with radiation treatment with or without surgical resection. However, these lesions will progress to multiple myeloma in 55% to 60% within 5 years, and untreated multiple myeloma has median survival of only 6 months.

Ewing Sarcoma

Ewing sarcoma was first described in 1921 by Sir James Ewing. It is the most common malignant primary spinal tumor of childhood and has a male predominance with peak incidence in the second decade. The most common site of occurrence is the sacrum.

Laboratory studies include alkaline phosphatase and lactic dehydrogenase levels. On imaging studies, an eroded vertebral body or “moth-eaten” lesion with a large, pathognomonic paraspinal soft-tissue mass is typically seen. Neurologic compromise will be evident in 58% to 64% of patients. MRI of these tumors tends to enhance with contrast because of the vascularity of the lesion. Additional studies should include technetium bone scan, full-body CT, or positron emission tomography (PET) scan to evaluate for metastatic lesions.

Neoadjuvant chemotherapy is as critical as the tumor’s response to the therapy. Surgical excision should be considered, followed by chemotherapy and potentially radiation therapy in certain cases. A recent study by Boriani and colleagues concluded that wide en bloc resection leads to better local control and longer survival ( Fig. 64-4 ). With a combination of aggressive chemotherapy and surgical resection, the 5 year survival rate approaches 60%.

Chondrosarcoma

Chondrosarcomas arise from mesenchymal cells as primary malignant tumors or as a secondary transformation from osteochondromas. They are the second most common primary vertebral column tumor of the non-myeloproliferative tumors, and they originate in the spine in about 12% of cases. Middle-aged men in their fifth or sixth decades are affected twice as often as women and have a propensity for lesions in the thoracic spine.

Radiographically, chondrosarcomas are expansive osteolytic lesions with diffuse, mottled “ring and arc” calcifications and associated soft-tissue mass as a result of the mix of chondroid (cartilage) and osteoid (bone). Similar to chordomas, chondrosarcomas are both hypointense and hyperintense on T1- and T2-weighted MR images, respectively, but do not usually arise in midline locations.

CT-guided biopsy will help determine the aggressiveness of the tumor, which is graded from 1 to 4 (most malignant). Complete en bloc surgical resection offers the best survival; however, survival is primarily determined by tumor grade. The 5 year survivals for low- and high-grade chondrosarcoma are 65% to 85% and 15%, respectively. Radiation therapy and chemotherapy are ineffective treatments.

Osteosarcoma

Osteosarcoma originates from primitive bone-forming mesenchymal cells. It is the third most common primary spinal tumor and the most common primary bony tumor in young patients (first to third decade). They may occur with increased frequency in patients with a history of Paget disease, trauma, or irradiated bone.

On presentation, a palpable mass is often identified, and neurologic deficits are present in 70% to 80%. In contrast to some of the other lesions, this tumor demonstrates osteoblastic changes, and primitive osteoid is seen on pathology. MR images display hypointensity and hyperintensity on T1- and T2-weighted images ( Fig. 64-5 ).

Historically, prognosis for osteosarcoma was poor, and the treatment of choice was wide en bloc resection. However, with advancements in adjuvant therapies and aggressive resection combined with neoadjuvant chemotherapy and radiation therapy, the prognosis has improved over the years (68% 5 year survival).

Chordoma

Chordomas arise from the remnants of the notochord and are a locally aggressive but exceedingly rare tumor. They constitute only 2% to 4% all primary malignant tumors and are more common in men; they typically occur in the fifth or sixth decade of life. The most common tumor sites include the cranium, sacrum, and the rest of the spine, equally distributed in the Surveillance Epidemiology and End-Results (SEER) study. Initial symptoms may include sensation of rectal fullness with large sacrococcygeal lesions in addition to spinal pain and potential for neurologic deficits from neural element compression.

Grossly this tumor is appears as a lobulated, gelatinous mass; on radiographs, it appears as a midline, destructive lytic lesion ( Fig. 64-6 ). A CT-guided biopsy should be performed for diagnosis (see Fig. 64-1 ). Under the microscope, these tumor cells have characteristic “soap bubble” or physaliphorous cells because of the vacuolated cytoplasm. On MRI, the lesion usually has a low intensity on T1-weighted images, and it is hyperintense on T2-weighted images because of its high water content. The contrast enhancement of this lesion varies ( Fig. 64-7 ).