Spinal tumor is abnormal growth developing either in or around the spinal column, spinal cord or spinal nerves.
Human spine or spinal column is composed of 33-34 vertebral bones staying on top of each other. In sacrum and coccyx vertebra are fused together but in other parts they are connected by joints. Spinal cord is located inside the spinal column and is surrounded by strong bones and ligaments. Therefore, spine has two main functions: providing protection for the spinal cord and supporting the body weight. Spinal cord is connecting the brain with the rest of the body by many nerves coming out of it ang traveling to all parts of the body.
Tumor is an abnormal growth caused by genetic mutation. All the cells in human body have a very peculiar genetic system for controlling growth and differentiation. Loss of this control causes cells to uncontrollably divide and cause tumor. Traditionally tumors can be divided into two main groups: benign and malignant. Benign tumors grow from "inside". They are basically an abnormally expanding structure that pushes nearby structures as it grows. They develop well defined border from normal tissue and thus surgical removal is relatively easy. Total tumor removal usually provides cure for these patients.
Malignant tumors on the other hand, are invasive. Tumor cells dislodge from the original location and invade nearby tissues. Therefore, the border between the tumor and normal tissue is poorly defined. Complete surgical elimination must include removal of some normal tissue around the tumor with may lead to loss of function. Malignant tumors may spread to surrounding tissued via direct invasion. Also, they may use lymphatic and blood vessels. This condition is called metastasis. Metastasis is very difficult to treat since surgery and radiation are of limited use.
Spinal tumors may arise either from spinal cord and nerves or spinal column. Spinal cord and nerves consist of nervous tissue and therefore tumors arising from them belong to neural lineage. Spinal column on the other hand, is composed of bone and connective tissue. Thus, tumors arising from it belong to bone/connective tissue lineage and have completely different biological features.
Tumors arising from neural tissue are usually benign and may originate from the spinal cord itself, spinal nerves or covers. Tumors located outside of the spinal cord are called extramedullary. They are generally easier to remove than tumors located inside of the spinal cord – intramedullary. For example, meningiomas are benign tumors originating from the spinal cord cover. They are extramedullary, benign, slowly growing tumors compressing the spinal cord from outside. On the other hand, benign tumors like ependymomas and astrocytomas originate from the spinal cord itself (intramedullary) and therefore are more difficult to separate and remove.
Spinal cord and nerves are covered by a protective cover named dura mater. Tumors may be located inside this envelope or outside it. Therefore tumors can be either extradural – outside the covers or intradural – inside the cover. Meningioma for example, is located inside the cover and therefore is intradural. Schwannomas and neurofibromas are benign tumors originating from the spinal nerves. If the tumor arising from the section of the nerve outside the cover it is called extradural. Schwannomas may be intradural or intra/extradural depending on the size and location. Sometimes they have dumbbell shape with two sections representing intra- and extradural sections. Malignant tumors can also affect the spinal cord and the nerves but they are very rare.
Spinal column tumors arise from the vertebral bones. These tumors are classified into two main groups: primary and metastatic. Primary bone tumors develop from the bone or connective tissue comprising the spinal column. They can have benign, malignant or mixed behavior.
Primary bone tumors
Hemangioma - the most frequent bone lesion is spine. In the vast majority of cases it is located inside the vertebral body and do not cause any symptoms. Rarely it can lead to bone destruction with collapse or may extend into spinal canal compromising spinal cord and/or the spinal nerves
Osteoid osteoma and osteoblastoma – are identical tumors but osteoid osteomas are small (less than 1 cm). If tumor is more than 1 cm it is called osteoblastoma
Osteochondroma or enchondroma – benign tumors orginating from cartilage tissue in the spine
Aneurysmal bone cyst – are considered benign tumors however, tend to recur after incomplete removal.
Osteosarcoma – the most frequent primary malignant bone tumor of the spine. Surgical removal is the cornerstone of the treatment. The best results are achieved with total removal since residuals (tumor leftovers) are resistant to chemotherapy and radiation treatment.
Chondrosarcoma – is also a malignant tumor originating from cartilageous tissue. Like osteosarcoma it is resistant to chemo- and radiotherapy and surgical removal is the main treatment option
Multiple myeloma and solitary plasmacytoma – are tumors arising from the bone marrow. They are the same tumors but plasmacytoma occur in one location. If the tumor is encountered in many locations it is called multiple myeloma. Usually these tumors are treated with chemotherapy and radiation. Surgery is reserved only for cases when bone fracture is present causing instability or spinal cord compression is evident.
Metastatic bone tumors
Metastatic tumors on the other hand, are extension of other cancers into the bones. They comprise the vast majority of spine tumors. Technically bone metastases occur in the bone marrow rather than bone tissue itself. Since spine contains almost the third of total body bone marrow it is the most frequent bone metastasis site. Cancer cells dislodge from the main tumor site and are spread to spine by blood flow. This process is called hematogenous metastasis. In some cases the main tumor does not produce symptoms and tumor is first discovered in spine.
Metastatic tumors can cause destruction of the tumor (osteolytic) or promote bone formation (osteoblastic). In some cases tumor may have both osteolytic and osteoblastic features. Generally, osteolytic tumors are more dangerous since they weaken the bone and cause fractures.
The most common symptom of spine tumors is pain. The pain is usually located at the involved site but may radiate to different parts of the body if nerves and spinal cord are involved. Pain may be very significant if tumor is causing bone destruction and fracture. This type of fracture is called pathological and may cause excruciating pain.
Neurological deficit may be present if tumor of fractured bone parts compress the spinal cord and nerves. Usually patients develop numbness, weakness (paralysis), ataxia (loss of balance), inability to control bowel movements and urination.
Diagnostic evaluation starts with throughout history and physical evaluation. It provides important information about possibility of cancer like weight loss or smoking habit. Assessing neurological status is very important since the patient may not be aware of ongoing neurological deficit or may think that it is irrelevant.
Spine imaging is a key element in diagnostic work-up. Magnetic resonance imaging (MRI) of the spine with intravenous contrast is the most preferred modality. It usually sufficient to demonstrate presence and extend of the tumor as well as its relationship with spinal cord and nerves. Computerized tomography (CT) and X-rays can show bone structures better than MRI.
For patients with suspected metastasis positron emission tomography (PET) can demonstrate the main tumor as well as other metastasis if present. Lab tests with tumor markers may be necessary to assess the extend of tumor. In some cases a biopsy from easily reachable area can be performed in order to establish the diagnosis.
Management of spinal tumors is highly specific. The most important aspect is the pathological diagnosis of the tumor. In some cases the diagnosis is very straightforward and the treatment is well known. In other cases extensive work-up may be required to reveal the nature of the tumor.
There are three options available for the treatment: surgery, chemotherapy and radiation therapy. Choice of treatment depends on sensitivity of tumor to chemo- and radiotherapy and feasibility of surgical removal.
Primary spinal cord and bone tumors are usually treated with surgery. It allows removal of the mass effect, obtaining tissue for pathological diagnosis and proving stability to spine, if needed. Completely removed benign tumors do not require further therapy. Malignant tumor may require adjuvant chemo and radiation treatment following the surgery. Surgical removal maybe very challenging since tumor maybe hard to separate from the spinal cord and nerves. Therefore, it should be performed by experienced surgeon.
Management of metastatic tumors depends on the type and stage of the tumor. Once these patients were considered inoperable terminal patients. However with modern therapeutic modalities most of this patients undergo surgery with adjuvant chemo and radiation therapy. The goal of surgery is relieving the pressure from the spinal cord and nerves and providing stability to the spine if compromised.