Lymphoma is a cancer that arises from lymphocytes, a type of white blood cell. Although most lymphomas begin in the lymph nodes, the condition can start anywhere in the body. Primary lymphoma of bone (PLB) starts in bone marrow, the spongy tissue inside most bones. PLB is very rare, accounting for only about 3 percent of all malignant (cancerous) bone tumors.
In most cases, treatment for PLB involves a combination of chemotherapy and radiation.
The Role of Lymphocytes
Lymphoma is a type of cancer that originates in white blood cells called lymphocytes. Lymphocytes are part of your body's immune system. The two main types of lymphocytes are:
- T lymphocytes (T cells)
- B lymphocytes (B cells)
Both T cells and B cells have specialized roles in helping your body fight infection.
Types of Lymphoma
Lymphoma is classified as one of two main types, based on whether or not certain unique cells (Reed-Sternberg cells) are present when the tumor is viewed under a microscope.
The two main types of lymphoma are:
- Hodgkin's Lymphoma
- Non-Hodgkin's Lymphoma
Both types of lymphoma are then broken down by doctors even further, based on whether the tumors originate in the body's T cells or B cells.
Most cases of primary lymphoma of bone are a type of non-Hodgkin's lymphoma of B cell origin called "Diffuse Large B Cell Lymphoma (DLBCL)." The remaining cases are due to a variety of other lymphoma types.
Primary Lymphoma of Bone
Primary lymphoma of bone is very rare. Cancers that start elsewhere in the body and then metastasize (spread) to bone are much more common than tumors that actually start in bone.
Patients with PLB may have one or more destructive bone lesions. These lesions can occur in any bone, but most commonly occur in bones with red bone marrow. This includes:
- Flat bones—such as the pelvis, spine, and ribs
- Long bones—such as the femur (thighbone) and humerus (upper arm bone)
PLB can occur at any age, but is more common in people over the age of 30. It affects more men than women.
The cause of PLB is not fully understood by doctors, but patients who are infected with certain viruses (HIV and Epstein-Barr) and those who have had an organ transplant are at increased risk for developing the condition.
Pain is the most common symptom of PLB. This pain is felt even at rest. Some patients may have swelling or feel a mass in the area of the tumor.
Because PLB destroys healthy tissue and weakens the bone, some patients may develop pathologic bone fractures in the area of the tumor. This is more common if the tumor develops in weight-bearing areas of the skeleton like the pelvis, spine, or femur (thighbone).
Other symptoms of PLB may include:
- Feeling ill
- Night sweats
- Weight loss
In rare cases, neurologic symptoms can develop if a tumor on the spine compresses the spinal cord. Neurologic symptoms may include:
- Shooting pain
- Numbness or tingling in the legs
- Bowel or bladder incontinence
Your doctor will talk with you about your general health and medical history and ask about your symptoms.
He or she will then examine the painful area, looking for:
- Tenderness over the bone
- Swelling or a mass
- Enlarged or hard lymph nodes
Your doctor will use imaging studies and other tests to help diagnosis primary lymphoma of bone.
X-rays. X-rays provide images of dense structures, such as bone. An x-ray of PLB will reveal a mottled appearance in the inner part of the bone. There may also be erosion of the hard outer part of the bone, noncalcified soft tissue masses, or widening of the diaphysis (long part of the bone) due to tumor expansion.
The results from your x-rays will help your doctor determine if other types of imaging studies are needed.
Other imaging studies. If your doctor needs more information, he or she may order additional imaging studies to help evaluate the tumor.
Other imaging studies may include:
- Computerized tomography (CT) scan
- Magnetic resonance imaging (MRI) scan
- Positron emission tomography (PET) scan
These studies can help your doctor determine if the cancer has spread to other parts of your body or expanded into nearby soft tissues.
Blood tests. Your doctor may order blood tests to check for abnormalities in the types and numbers of different cells within your blood. Possible findings include anemia (low red blood cell count) or thrombocytopenia (low platelet count).
Biopsy. A definitive diagnosis of primary lymphoma of bone is made with a bone biopsy. In a bone biopsy, a small sample of the tumor is removed and examined under a microscope.
The procedure can be performed under local anesthesia with a needle or as a small open operation.
When viewed under a microscope, the typical appearance of lymphoma includes many small round blue cells.
Once your tumor has been identified as PLB, your doctor will conduct more tests to "stage" the tumor.
Tumor stage is determined by a number of factors, including:
- The size and location of the primary tumor
- Lymph node involvement
- Whether the cancer has metastasized (spread)
Identifying the stage of the tumor will help your doctor determine the most effective treatment strategy.
Treatment for PLB almost always includes some combination of multi-agent chemotherapy (CHOP—cyclophosphamide, doxorubicin, vincristine, and prednisone), either with or without radiation. The exact combination of agents used will depend on the results of imaging studies and the stage of the tumor.
An additional agent that specifically targets tumor cells, such as rituximab, may also be added.
Surgery to remove the tumor is generally not performed; however, some patients may need surgery to stabilize the affected bone if a pathologic fracture has occurred or could potentially occur in the future. Your doctor will use metal rods or plates and screws to fix a fracture or prevent bone breakage before it occurs.
Your outcome after treatment will depend on a number of factors, including:
- Your age
- The size, location, and stage of the tumor
- The method of treatment
After treatment, you will meet with your doctor so that he or she can assess your response to therapy. Regular follow-up appointments are needed to ensure that there are no treatment complications and that the tumor has not recurred. Recurrence can occur even many years after treatment, so close follow up is necessary for all patients diagnosed and treated for lymphoma.
The prognosis for patients with primary lymphoma of bone is highly variable, but most tumors respond to multi-agent chemotherapy with or without radiation. Your doctor will talk to you about your specific prognosis.
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