Diagnosis and Surgical Staging of Spinal Tumors The introduction of oncological principles and methods in the diagnosis and treatment of spinal tumors has been a notable advancement for more than 20 years. A positive attitude toward malignant tumors of the spine, especially metastatic tumors of the spine, is an important diagnostic and treatment concept. Surgical staging of the spine based on oncologic principles is an important guideline for the surgical management of spinal tumors. The basic diagnostic principle of spinal tumors is the combination of clinical, imaging and pathology. The most important steps in diagnosis are to distinguish: (1) tumor and non-tumor diseases; (2) benign and malignant tumors; (3) primary and metastatic tumors. Incidence: It is generally believed that the incidence of bone tumors accounts for 1～2/10,000 of systemic tumors, and spinal tumors account for 6.6%～8.8% of systemic bone tumors. Various types of bone tumors can be seen in the spine, of which spinal metastatic tumors account for more than half of them. Tumor statistics show that the ratio of benign and malignant tumors is 1:4-5, and the incidence of male and female tumors is roughly the same. Dahlin reported a group of 6221 cases of bone tumors, of which 548 cases were located in the spine, accounting for 8.8% of the total body of primary bone tumors, of which 105 cases were benign, accounting for 19.2%, with giant cell tumor of bone as the most; 443 cases were malignant, accounting for 80.8%, with myeloma as the most. The analysis of 38359 cases of bone tumors in China, such as Huang Chengda, showed that: 21691 cases of benign bone tumors, 584 cases of benign spinal tumors, a total of 17 kinds, the first three cases were osteoblastoma, osteochondroma, osteoangioma; 10791 cases of malignant bone tumors, 1243 cases of malignant spinal tumors, a total of 24 kinds, the first three cases were metastatic tumor of the spine, osteomyeloma, chordoma; verrucous lesions, 43 69 cases, of which 43 69 cases occurred in the spine, of which 43 69 cases occurred in the spine. 43 69 cases, of which 109 cases occurred in the spine, mainly eosinophilic granuloma, aneurysmal bone cyst, and osteofibrous dysplasia. The incidence rate of spinal tumors is not high, but there are many types of spinal tumors, and the anatomical relationship of the spine is complicated, which brings many difficulties in diagnosis and treatment. Among the clinical manifestations of spinal tumors, apart from neck, chest and lumbar back pain, they are mainly symptoms and signs caused by compression or invasion of spinal cord and/or nerve roots. (According to Dahlin’s report, nearly 8% of primary benign bone tumors are located in the spine or sacrum, and their age of onset is mostly seen in adolescents; 60% of spinal tumors occur between 20 and 30 years old. Benign tumors and tumor-like lesions of the spine have mild symptoms and a long history, and may remain asymptomatic for long periods of time. Some of these tumors are detected on radiographs after minor injuries, such as osteochondromas and osteoangiomas, which may remain asymptomatic for a long period of time. The most common complaint is pain, limited or radiating. Osteoid osteoma and osteoblastoma are often characterized by nocturnal pain, which can be relieved by salicylic acid. Back pain in children is rare, and this complaint should be taken seriously. It is generally believed that pain after minor trauma should be noted as a possible benign tumor. Intervertebral disc herniation is also rare in children and adolescents, and if there is radicular pain, tumor-induced possibilities should also be excluded. It has been observed that 37% of benign tumors of the cervical spine have radicular pain. Among the signs of benign spinal tumors, local pressure pain is not specific, and attention should be paid to the presence or absence of scoliosis, which has the following characteristics: rapid development of scoliosis with pain; stiffness of spinal movement; absence of compensatory balanced curvature above and below the curvature of the lesion; and absence of vertebral rotation and wedging on X-ray film. These are different from idiopathic scoliosis. About 1/3 of tumors occurring in the cervical spine present as a strabismus. When the tumor compresses or has a pathological fracture and affects the neural structures, it will produce neurological signs, such as radicular pain and corresponding signs of impaired neurological function, as well as myelopathic manifestations of impaired spinal cord function, such as altered sensation, movement, reflexes, and conotruncal fasciculations, etc. Especially tumors of cervical and thoracic vertebrae are prone to cause impairment of the spinal cord function. Spinal masses are most easily found in the cervical and sacrococcygeal regions and are easier to palpate than those in the thoracic and lumbar regions. Careful palpation and oropharyngeal examination are needed, and anal examination should also be performed. (Malignant primary spinal tumors are rare, accounting for 1/40 of the common metastatic spinal tumors. However, 80% of spinal tumors in adults are malignant. The main clinical manifestation is pain, with nocturnal pain being a common complaint. The pain is sometimes related to activity, but when the tumor causes a pathological fracture, the pain is not related to activity and is not relieved by rest. When the nerve roots are affected, persistent back pain and radicular pain may occur. Tumors of the cervical and lumbar spine are associated with unilateral radicular pain in one-fifth of cases, while tumors of the thoracic spine tend to cause spinal cord compression and/or bilateral radicular pain. The main signs are caused by the compression of the spinal cord or nerve roots by the tumor. The main signs are weakness of limbs, spasm, corresponding sensory loss, and even loss of bowel control. The neurological manifestations are different according to the location of the spinal lesion. If the spinal cord is compressed, there are corresponding signs of upper motor neuron damage; if the lesion is below the cauda equina, there are signs of lower motor neuron damage. Although these signs are not specific, they are useful in determining the location of nerve damage. Malignant primary spinal tumors may also present with systemic symptoms, such as myeloma, lymphoma, and Ewing’s sarcoma, with weight loss, low-grade fever, and generalized malaise, and malignant disease may be seen in advanced stages. Localized lumps can also be seen, such as cervical chordoma can be found in the pharynx, sacrococcygeal chordoma can be found in the anus. (The most common sites of cancer metastasis are lungs, liver and bones, among which the spine is the most common site of bone metastasis. Shaw et al. estimated that of the 1 million new malignant tumors diagnosed each year, 2/3 have metastasized. Breast, prostate, lung, and kidney cancers are the most common tumors that metastasize to the skeletal system. The majority of patients with metastatic tumors are between 50 and 60 years of age, with no difference in gender. Almost all patients with spinal metastases have pain at the time of diagnosis, but in the early stages, some patients have no obvious discomfort. The pain occurs gradually and is often worse at night. As the disease progresses, the pain worsens and becomes a burning pain. When the stability of the spine is compromised, pain with movement occurs, and unilateral or bilateral radicular pain occurs. In 5% of patients with spinal metastases, pain is associated with neurologic dysfunction. In cervical and lumbar metastases, neurologic deficits appear later, whereas in thoracic metastases, neurologic deficits appear soon after the onset of pain. Depending on the plane of neurologic dysfunction, symptoms of the spinal cord, cones, and cauda equina may appear, and motor dysfunction is the most common sign, while lower motor neuron paralysis may appear in conical metastases, and sensory deficits usually appear after motor dysfunction. Sphincter dysfunction often occurs at a later stage, mostly due to pathologic fracture and rarely alone. Diagnostic tools (I) Benign spinal tumors 1. X-ray: (1) Some tumors have the tendency to develop in a certain part of the vertebrae: for example, if the tumor mainly invades the posterior vertebral structure, there are osteoblastoma, osteoid osteoma, aneurysmal bone cyst and osteochondroma; if the tumor mainly invades the vertebral body, there are giant cell tumor of bone, bone hemangioma and eosinophilic granuloma. ( 2 ) Some characteristic X-ray manifestations: osteoid osteoma and osteoblastoma have round or oval foci at the vertebral arch root with sclerotic changes surrounding them; hemangioma shows thickening of bone trabeculae with fenestrated changes; eosinophilic granuloma shows flat vertebrae; aneurysmal bone cysts and osteoblastomas are expansive osteolytic changes. 2, bone scan: bone scan is highly sensitive, can observe the whole body bones, but the specificity is not strong, only suitable for determining the lesion site, for adolescent painful scoliosis, in the case of no abnormality in X-ray examination can choose bone scan. Bone scans are useful in the diagnosis of osteogenic lesions such as osteoid osteoma and osteoblastoma. It should be noted that bone hemangiomas may not have nucleosome concentration in the diseased vertebrae on bone scan; most of the spinal bone metastases show nucleosome concentration on bone scan; positive bone scan suggests that the tumor is biologically active or invasive; positive bone scan of osteochondroma with clinical pain should be noted for malignant transformation. 3. CT and MRI: CT has good ability to distinguish bone structure and MRI has good ability to distinguish soft tissue. After X-ray or bone scanning to determine the site, CT should be the first choice to determine the scope of the lesion, and in addition to the axial cross-section of CT to observe the bone structure, sagittal and coronal reconstruction of CT is more conducive to the determination of anatomical location and scope of the lesion. In addition, MRI can be used to observe whether the tumor has penetrated the osteodermis, the extent of soft tissue invasion, and whether it has affected the neural structures. Since MRI is also a sensitive examination tool, osteoid osteoma, osteoblastoma, eosinophilic granuloma, etc. are often found, and the lesions on MRI images are larger in extent than those on CT images, with T2-phase high signals, which may be due to inflammatory reactions in the soft tissues around the lesions. We have observed two cases in which it took 1 to 2 years for the high signal reaction to disappear. 4. Vertebral lesion biopsy: except for a few typical lesions, most spinal tumors still cannot be diagnosed clearly by imaging and bone scanning alone. In order to make treatment plan, it is necessary to achieve qualitative diagnosis before operation, and the most direct method is CT-guided biopsy. 5. Laboratory tests: routine laboratory tests are necessary as part of the treatment routine, but all laboratory tests are not directly helpful in the diagnosis of spinal tumors, especially benign spinal tumors. (ii) Malignant spinal tumors: 1. X-ray: (1) Clear X-ray film is needed. Malignant tumors are more common in lesions located in the anterior part of the vertebral body. Benign tumors growing on the vertebral body commonly include hemangiomas, eosinophilic granulomas, and aneurysmal bone cysts; malignant tumors growing on the vertebral body include chordomas, lymphomas, and osteosarcomas, and so on. Tumors located in the posterior vertebral structures include osteochondroma, osteoid osteoma, osteoblastoma, and chondrosarcoma. ( 2 ) Observation of osteolysis, osteogenesis, calcification in the vertebral body, and involvement of the intervertebral disc are important differential diagnostic clues. Infiltrative destruction is the growth mode of most malignant tumors, and there is no sclerotic margin in the destroyed vertebral body. In the early stage of lesions and slow-growing tumors, the bone of vertebral body can be fan-shaped or swollen, if there is no sclerosis around the lesion or the edge of sclerosis is very thin and incomplete, it also suggests that the invasiveness of the tumor. 2. Bone scan: there is nuclide concentration in all bone formation sites, osteogenic tumor, bone healing process and bone infection all have nuclide concentration phenomenon, so bone scan cannot distinguish tumor from non-tumor, and cannot distinguish benign and malignant nature of tumor. When there are multiple nuclide concentrations, spinal metastases should be considered. For myeloma of the spine, it is generally believed that there is no osteogenic process in the lesion, so the lesion appears as a cold zone on bone scan, and this phenomenon is also occasionally seen in chordoma. Because bone scan is very sensitive, the lesion can be detected before the X-ray becomes abnormal, and the whole body can be scanned, so it can be used as an important means of diagnosis. 3. CT and MRI: CT can provide information about the extent of bone destruction, border, pathological fracture, osteogenesis and calcification within the tumor, and is better than MRI in understanding the pathological changes of bone structure. MRI is superior to MRI in showing the soft components of the tumor and the involvement of the surrounding soft tissues, and can clearly show the spinal cord and nerve roots as well as the extent of tumor invasion. MRI can also help to distinguish between tumor, infection and fracture: in spinal osteomyelitis, the T2-weighted image of the vertebral body is high signal, which can show the involvement of vertebral cartilage endplates, intervertebral discs and adjacent vertebral bodies, while the T1-weighted image of the vertebral body and intervertebral discs is low signal; in osteosarcoma, the T2-image of the vertebral body is enhanced, while the T1-image is weak and strong and the intervertebral discs are low signal; the compression fracture of osteoporosis still retains the signal intensity of the bone, and if a fresh fracture causes bleeding or hematoma, then MRI is more useful for the detection of tumor and infection. If a fresh fracture causes hemorrhage or hematoma, it is difficult to distinguish it from a tumor on MRI. MRI combined with CT is valuable in determining the extent of the tumor, guiding the treatment plan and determining the surgical approach. 4. Biopsy: (the same as “benign spinal tumor”) 5. Laboratory examination: In order to complete the examination and understand the patient’s general condition, routine examination is necessary. For diagnosis, there are alkaline phosphatase, acid phosphatase, urine Ben-Zhou protein, etc. Bone marrow aspiration should be performed if necessary. (C) Spinal metastatic tumor: 1, X-ray: the common X-ray sign of spinal metastatic tumor is the disappearance of the vertebral arch root on the orthopedic film of the spine, which is called Owl wink. In general, it is believed that more than 30%-50% of the vertebral body has been destroyed before bone destruction can be detected on X-ray. Bone metastases should be considered when there are multiple vertebral bodies with osteolytic changes. Seventy-one percent of spinal metastases are osteolytic, 8 percent are osteogenic, and 21 percent are mixed. Vertebral collapse may be caused by metastasis. According to a study, 22% of vertebral collapse in patients with diagnosed malignant tumors was not caused by the tumor, so it needs to be carefully identified. 2. Bone scan: Because bone scan reflects the activity of osteoblasts rather than the proliferation of tumor cells, there will be aggregation of nuclides only when the bone destruction caused by the tumor has a repair reaction similar to that of fracture. In highly aggressive metastatic tumors, such as kidney cancer, lung cancer, multiple myeloma, leukemia, lymphoma, Ewing’s sarcoma, etc., the host’s resistance is not as strong as the tumor’s invasive ability, and it cannot produce reactive new bone, and then the bone scan can also be negative. Since bone scan can examine bones of the whole body with high sensitivity and can be detected 2-18 months before the lesion is found by X-ray, it is very valuable for the diagnosis of metastatic tumor. 3. The application value of CT and MRI is the same as that mentioned before. CT cannot show the whole spine, therefore, it is possible to miss the diagnosis of asymptomatic patients with CT examination, and according to the study, the percentage of missed diagnosis is 20%～24%, which should be emphasized. MRI provides more complete information for the diagnosis of spinal metastases. When vertebral metastases are present, the T1-weighted image is low-signal and the T2-weighted image is enhanced. MRI can detect lesions >3 mm. If gadolinium-enhanced MRI is used, the metastatic foci can be better visualized. In addition, this type of enhanced MRI can be used to evaluate the effects of radiotherapy and chemotherapy on spinal metastases, and 70% of those who were treated effectively did not have enhancement, so it is clear that what is seen on the enhanced MRI is more consistent with the effects of treatment. Compared with myelography, MRI is superior in that it can show the soft tissue boundaries and paravertebral masses more comprehensively, and can distinguish the part of spinal cord compression, while myelography cannot show clearly when the spinal cord is completely obstructed or when there are more than two lesions. 4. Spinal biopsy: When spinal lesions are atypical on imaging, and the clinical history and physical examination cannot provide more information for differentiation, it is necessary to perform a spinal biopsy. X-ray or CT-guided spinal biopsy has been successfully experienced at home and abroad, with a success rate of about 95% in diagnosing metastatic tumors, and complications such as intraoperative or postoperative hemorrhage of 0.7% in biopsy, and in 9500 bone biopsies in the literature reviewed by Murphy et al., the complication rate was 0.2%, with 2 deaths and 4 cases of neurological dysfunction. 5. Laboratory examination: besides routine laboratory examination to evaluate patients’ nutritional status, immune status and other systemic conditions, it is more meaningful to pay attention to hypercalcemia in bone metastasis of malignant tumors; alkaline phosphatase is elevated in osteogenic bone metastasis, but seldom elevated in myeloma; serum acid phosphatase can be used as an indicator for prostate cancer, but it is more sensitive to prostate-specific antigen. Other tumor markers, such as carcinoembryonic antigen, are not specific, but also helpful. Differential diagnosis of benign and malignant spinal tumors (1) The requirement of differential diagnosis is to distinguish the following three aspects: 1. Whether it is a spinal tumor or not. Whether it is a spinal tumor or not. Distinguish the tumor from inflammatory diseases of the spine, such as tuberculosis, nonspecific inflammation of the bone, parasitic diseases of the spine, and metabolic bone diseases involving the spine. 2. Is the tumor benign or malignant? 3. If it is a malignant tumor, it should be distinguished as primary or metastatic. (Surgical staging of spinal tumors Surgical treatment of spinal tumors is very demanding, for example, adequate exposure, extensive resection and decompression, reconstruction of spinal stability, and so on, and there are specific problems to be studied at each step. In recent years, there has been great progress in the surgical treatment of spinal tumors. In short, the WBB spinal tumor staging has been used to guide the surgical treatment of spinal tumors under the guidance of Enneking’s staging of musculoskeletal tumors. The surgical staging system proposed by Enneking is valuable in guiding the treatment of bone and soft tissue tumors, and this system has 3 basic requirements: grading ( G ), site ( T ) and metastasis ( M ). It is based on histologic criteria, plus clinical and radiographic findings. Low malignancy is classified as G1 and high malignancy as G2; the surgical site (T) is categorized as interstitial (A) and extra-interstitial (B). If the tumor has a natural barrier, such as bone, fascia, synovium, periosteum, or cartilage, it is interstitial. Extra-interstitial tumors may be primary (originating outside the interstitial compartment) or secondary (originally intra-interstitial tumors that extend through the natural barrier or pass through another compartment as a result of surgery or biopsy). If there are regional lymph nodes or distant metastases, the tumor is stage III. In conclusion, the Enneking system suggests that a lesion may be stage I or II depending on its grade, A or B depending on its location, and stage III as metastatic. Later, benign tumors were also staged and considered to have some clinical significance. The staging system for benign lesions is: stage 1 is benign and delayed (S1); stage 2 is active (S2); and stage 3 is invasive and potentially malignant (S3). Enneking’s surgical staging of bone and soft tissue tumors is very meaningful in guiding the treatment decision of limb tumors, evaluating the therapeutic effect, and judging the prognosis, and has been confirmed by clinical practice. Due to the complex anatomical relationship of the spine, it is difficult to implement Enneking’s surgical staging principle in the surgical treatment of spinal tumors. For example, in Enneking staging, there are the concepts of marginal resection, wide resection and radical resection, which are easy to understand and realize for limb tumors, but not easy to grasp for spine tumors. Moreover, in the past clinical practice, we often encountered the scraping of certain spine tumors, and we even thought that scraping surgery is unavoidable, which is a complete deviation from the staging principle of Enneking. This is a complete departure from Enneking’s staging principle. In 1991, Weinstein firstly proposed a staging method for primary spinal tumors, which was subsequently improved continuously. At present, the WBB staging system for primary spinal tumors, named by three authors, Weinstein-Boriani-Biagini, has often appeared in the literature, and for the sake of convenience of narration, we refer to it as WBB staging in the present paper, which is briefly described as follows. 1. The guiding ideology of WBB staging WBB is established on the basis that the diagnosis of tumor is basically clear and the Enneking staging of tumor has been established. WBB staging method: according to X-ray, CT, and MRI images, the horizontal section of the vertebral body was divided into 12 radial regions (Sec tor), with the center of the vertebral canal as the round point, starting from the left posterior side, and then divided into 1 to 12 regions; meanwhile, the horizontal section was divided into 5 layers from the outer to the inner layers, A, B, C, D, and E. The A layer was the extra-osteosynovial soft tissues, the B layer was the superficial bone layer, the C layer was the deep bone layer, the D layer was the epidural layer, and the E layer was the extradural layer. B is the superficial layer of bone, C is the deep layer of bone, D is the epidural layer, and E is the intradural layer; in addition, the number of vertebrae involved is counted on the longitudinal axis of the spine. Accordingly, the spatial location and extent of the tumor and the adjacency of the involved segments are determined, and the surgical plan is formulated according to the spatial location and extent of the tumor. 2. Explanation of terms ( 1 ) Curettage: it means the tumor is scraped off piece by piece, and it is intralesional surgery. (2) En bloc resection: It means that the tumor and its surrounding healthy tissues are removed in one piece. En bloc resection does not necessarily mean complete removal of the tumor, so it should be defined according to the gross specimen and pathological examination as follows: 1) if the surgery is done within the tumor, it is still regarded as intralesional surgery; 2) if the resection is done along the pseudocapsule, which is the reactive layer of tissue surrounding the tumor, it is known as marginal resection; 3) if the tumor is removed together with a thin layer of healthy tissue in the surroundings, it is called extensive resection; 4) if the tumor is removed together with a thin layer of healthy tissue, it is considered as extensive surgery. (3) If the tumor is removed together with a thin layer of surrounding healthy tissue, it is called wide resection. (3) Radical resection: This refers to the complete removal of the tumor and the compartment where the tumor occurs. This is easy to implement for limb tumors, such as amputation, etc. However, it is not easy to implement for spinal tumors. However, it is not easy to realize for spinal tumors, because the spinal cord in the spinal canal cannot be removed, so complete resection in the true sense is not easy to realize in the treatment of spinal tumors. (4) Surgery for palliation: it refers to decompression of the spinal canal and stabilization of pathological fracture, etc. When this kind of surgery is performed, whether the tumor is removed or not is not the main purpose, but it aims to alleviate the pain. (5) Total vertebrectomy (vertebrectomy, spondylectomy, referring to the removal of all parts of a vertebral body) and somectomy (corporectomy, somectomy, referring to the removal of the vertebral body) belong to the anatomical concepts of the resection technique and are descriptions of the amount of resection. Care should be taken to clearly explain and qualify whether the tumor has been removed cleanly. When these terms are used, they should be defined in terms of gross specimen and pathologic observation, such as within lesion, border resection, wide resection, etc. Otherwise, it is also difficult to determine the amount of spinal cord resection. Otherwise, it is difficult to determine the significance of surgical treatment of spinal tumors. 3. Surgical selection of spinal primary tumors The surgical technique of vertebral body resection was reported by Lievre in 1968, and it was not until 1989 that Stener reported the whole body resection technique to remove spinal tumors. Later, Roy-Camille et al. also reported the lumpectomy technique, the posterior approach to remove tumors located in the thoracic vertebral body, and the combined anterior and posterior approach to remove lumbar spine tumors. Tomita et al. reported the experience of removing thoracic and lumbar tumors with a special saw. The WBB surgical staging method has brought the treatment of spinal tumors to a new level, guiding clinicians to perform en bloc excision according to the boundaries of tumor expansion or invasion, and proposing three methods of en bloc excision: (1) en bloc excision of the vertebral body: when the tumor is located in vertebral regions 4-8 or 5-9, and there is suitable space for the resection, it is necessary to use a special saw to remove the tumor. ～ (1) En bloc excision of the vertebral bocly: When the tumor is located in zones 4 to 8 or 5 to 9 of the vertebral body, and there are suitable margins, and there is no tumor invasion of at least one side of the vertebral root, the anterior approach can be used to reveal the vertebral tumor and excise it, and a thin layer of normal tissue around the vertebral body can be left. In order to achieve complete resection, two surgical approaches can be used if necessary. (2) Sagittal resection: When the tumor is located in zones 3-5 or 8-10, i.e., the tumor invades the vertebral root, transverse process, part of the ribs, part of the vertebral body, and part of the posterior arch, two approaches are used to perform a complete resection. The operation is done in two steps, the first step is to remove the vertebral body lesion through the anterior approach according to the vertebral body resection, and the second step is to remove the lesion at the vertebral root and transverse process with appropriate incision. (3) Resection of the posterior arch: When the tumor is located in zones 10 to 3, a posterior approach can be used to perform extensive laminectomy, with exposure on both sides to the vertebral roots and cephalad and caudal exposure of the dura mater at the site of the lesion. According to the WBB Staging Initiative, this approach was used to treat 29 cases of spinal tumors, of which 21 were surgically resected to achieve reasonable tumor margins, with no recurrence at a postoperative follow-up of 6 to 134 months. The authors concluded that WBB staging basically reflects the relationship between tumor grade, surgical technique, and outcome of tumor treatment. It should be said that the WBB staging method is by far a more perfect classification method to guide the surgical treatment of spinal tumors. In conclusion, reasonable surgical treatment of spinal tumors must consider three aspects, i.e., diagnosis, determination and staging of tumor margins, and strict surgical plan. To solve these three problems, at least two systems are needed, the first one is the staging of the tumor’s pathobiological behavior and the aggressiveness of the clinical process (guided by the Enneking staging); the second one is the definition of the tumor’s margins, the establishment of the spatial extent of the tumor and its adjacency, and the surgical resection of the tumor according to the WBB staging. Of course, tumor treatment also includes chemotherapy and radiotherapy, which are not mentioned here.