Primary spine tumors

1

What types of tumors arise in the spine?

Primary tumors and secondary tumors.

2

What is the difference between primary and secondary tumors of the spine?

Primary tumors of the spine arise de novo in the osseous, cartilaginous, neural, or ligamentous structures of the spine. They may be classified as extradural or intradural. Secondary tumors are either metastatic to the spine from distant origins or grow into the spine from adjacent structures, such as a Pancoast tumor from the upper lobe of the lung. Primary spine tumors are extremely rare. Metastatic lesions involving the spine are the most common type of spinal tumor and account for over 90% of all spinal tumors. To put these numbers in perspective, estimates are that one person per million has a primary spine tumor compared with 85 persons per million with a metastatic spinal tumor. Primary bone tumors of the spine are the emphasis of this chapter.

3

How are primary tumors of the spine classified?

Multiple classifications have been proposed for primary spine tumors. One method for classifying primary spine tumors is based on histology . The World Health Organization (WHO) developed a classification of bone tumors based on histomorphologic features, which was initially published in 1972 and has been updated periodically ( Table 62.1 ).

• Benign tumors are nonaggressive tumors that may be asymptomatic or may cause pain, local symptoms, or local tissue destruction. However, these lesions do not aggressively invade adjacent structures, have limited ability to recur, and do not metastasize (e.g., osteoid osteoma).

• Intermediate tumors may be categorized as locally aggressive (e.g., osteoblastoma, grade 1 chondrosarcoma) or locally aggressive with the capacity for distant metastases , most commonly to the lung (e.g., giant cell tumor [GCT] of bone).

• Malignant tumors of bone (also termed bone sarcomas ) cause local destruction, recur locally, and have the capacity to metastasize to other organs. These are life-threatening tumors by their fundamental nature (e.g., osteosarcoma, Ewing sarcoma).

Other categories of bone tumors in the WHO classification include tumors of undefined neoplastic nature and miscellaneous tumors .

4

Is there a relationship between age, location, and whether a spine tumor is benign or malignant?

Yes. There is a relationship between age at diagnosis and whether a tumor is benign. In patients younger than 18 years, 68% of all tumors are benign. If age at presentation is older than 18 years, more than 80% of all tumors are malignant. There is also a relationship between tumor location and whether a tumor is benign. Benign lesions tend to occur more frequently in the posterior elements (e.g., osteoblastoma, osteoid osteoma), whereas malignant lesions tend to involve the vertebral body.

5

What are some common spine tumor diagnoses according to patient age?

• 10–30 years: Langerhans cell histiocytosis (eosinophilic granuloma), osteoid osteoma, osteoblastoma, osteochondroma, GCT, aneurysmal bone cyst (ABC), osteosarcoma, Ewing sarcoma

• 30–50 years: chordoma, chondrosarcoma, hemangioma

• Older than 50 years: metastatic tumors, myeloma, lymphoma

6

What are some common spine tumor diagnoses according to location?

• Posterior spinal elements: osteoid osteoma, osteoblastoma, osteochondroma, ABC

• Vertebral body: chordoma, GCT, myeloma, hemangioma, Langerhans cell histiocytosis (eosinophilic granuloma), ABC, Ewing sarcoma, metastatic disease

• Involvement of both anterior and posterior spinal elements: osteosarcoma, chondrosarcoma, osteoblastoma, ABC, myeloma

• Involvement of adjacent vertebra: ABC, chondrosarcoma, chordoma, GCT, myeloma, metastatic disease

• Involvement of multiple vertebra: metastatic disease, Langerhans cell histiocytosis, myeloma

7

What is the most common clinical presentation of a primary spinal tumor?

Pain is the most common presenting symptom. Pain is frequently described as persistent, progressive, and not typically associated with activity. Pain at night is a characteristic symptom. Subjective weakness, radiculopathy, objective neurologic deficit, and bladder or bowel dysfunction may develop over time. Occasionally patients may present with a palpable mass, pathologic fracture or a painful spinal deformity. Pelvic girdle malignancies, including chordoma, osteosarcoma, chondrosarcoma, and malignant fibrous histiocytomas, may present with back pain and sciatica. Always remember to evaluate the pelvis if the spine appears normal or the degenerative lesion does not fit the patient’s degree of pain or neurologic involvement.

8

What are the initial steps in the evaluation of a patient with a newly diagnosed bone lesion involving the spinal column?

New bone lesions identified on plain radiographs have a long list of differential diagnoses, ranging in severity from developmental abnormalities or benign lesions to malignancies. The patient should be evaluated with a detailed and comprehensive medical history, family history, review of systems, physical examination, and radiographs. Patient history should include details regarding pain (if present), including its intensity, duration, and pattern. The examiner should inquire about any changes in bowel or bladder control, as well as any complaints of extremity pain, weakness, sensory changes, and gait or balance problems. Family history should address whether there is any history of benign or malignant tumors, common cancer risk factors, or conditions that alter bone development and/or metabolism. Physical examination should include a general survey and detailed neurologic examination. Initial lab tests to consider include a complete blood count (CBC), erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP) to rule out infection.

Plain radiographs are the recommended initial imaging modality. Review of plain radiographs by a fellowship-trained musculoskeletal radiologist can be used to initially triage lesions as nonaggressive/indolent versus other lesions that require additional imaging studies and referral. For example, for an asymptomatic patient diagnosed with a lesion that has all of the imaging characteristics of a benign lesion (e.g., vertebral hemangioma), observation is appropriate and no further workup or treatment is indicated. Lesions that are symptomatic or lesions with aggressive features on initial radiographs require further evaluation. Magnetic resonance imaging (MRI) is indicated if diagnostic uncertainty remains. Computed tomography (CT) may be considered if MRI is contraindicated.

If the patient with a painful bone lesion is less than 40 years old and initial lab tests and spinal MRI are not consistent with spinal infection, referral to an orthopedic oncologist to rule out a primary bone tumor is recommended.

If the patient is greater than age 40 years, metastatic carcinoma involving the spine is the most likely diagnosis. Workup for metastatic disease includes lab tests (CBC, ESR, CRP, comprehensive metabolic panel [CMP], serum protein electrophoresis [SPEP)], urine protein electrophoresis [UPEP], prostate-specific antigen [PSA] for males), CT of the chest, abdomen, and pelvis with contrast, technetium-99m ( ⁹⁹ Tc) bone scan, mammogram in females, and CT-guided biopsy of the spinal lesion.

9

What workup is required to stage a primary malignant tumor of the axial skeleton?

A comprehensive imaging evaluation and a biopsy of the lesion are required. In addition to plain radiography and MRI of the spine, additional imaging modalities that may be considered include CT (spine, chest), ⁹⁹ Tc bone scanning, 18-fluorine fluorodeoxyglucose ( ¹⁸ F-FDG), positron emission tomography (PET), and angiography.

Spine CT provides information regarding the extent of bone destruction and osseous architecture. Chest CT is used to assess for lung metastases. The presence of extrapulmonary bone metastases may be assessed with a whole body ⁹⁹ Tc bone scan. Alternative options for whole body screening include ¹⁸ F-FDG, PET/CT, and whole body MRI. Angiography is useful in specific situations, for example, to identify the anatomy and vascular supply to a tumor as an aid to surgical planning. In addition, preoperative angiography and embolization are used to reduce intraoperative blood loss and blood transfusion volume during the surgical treatment of highly vascular tumors such as GCT, ABC, osteoblastoma, chondroblastoma, and chondrosarcoma.

Biopsy is required to reach a histologic diagnosis and assess the tumor grade. Options for biopsy included CT-guided fine-needle aspiration, CT-guided core needle biopsy, incisional biopsy, and excisional biopsy. CT-guided fine-needle or core-needle biopsy are most commonly utilized for spinal lesions. The advantages of core-needle biopsy versus fine-needle biopsy include a larger sample of tissue and preservation of tissue architecture. Oncologic principles require that the biopsy technique minimize local contamination and the biopsy tract should be marked to allow for later excision if a definitive surgical resection is required.