Extramedullary plasmacytoma (EMP) is a rare cancer that forms from plasma cells (a type of white blood cell). Plasma cells function as part of the immune system and help the body fight infection by making proteins called antibodies. The abnormal growth and overproduction of plasma cells give rise to a group of cancers called plasma cell neoplasms, which includes EMP, along with other diseases like multiple myeloma. When the plasma cells form a single tumor in one area of the body, it is called solitary plasmacytoma. Multiple tumors indicate multiple myeloma.
EMP is a rare and complex disorder and requires treatment from a team of medical professionals including a hematologist (blood disorder doctor), occasionally a radiation oncologist (doctor specializing in radiation for tumors), and possibly an orthopedic surgeon.
EMP develops from abnormal plasma cells that form a tumor in a single location of the body. EMP is one of two types of solitary plasmacytoma — the other type is solitary bone plasmacytoma (SBP). The main difference between the two is that SBPs form in the bone and EMPs occur in soft, non-bony tissue. EMPs are typically found in the head and neck region, most commonly in the nasal cavity and throat. Less common locations for EMPs include the gastrointestinal tract, lungs, arms, and legs. EMPs are rarer than SBPs, making up only 30 percent of all cases of solitary plasmacytoma.
EMP is a very rare form of cancer, affecting fewer than 1 in 500,000 people and primarily older adults (55 to 65 years old). It is more common in men than women, and Black Americans have about a 30 percent higher rate of diagnosis than white Americans.
Symptoms of EMP can vary significantly depending on the location of the tumor. Symptoms are often related to pain and pressure from the growing tumor mass. Some reported symptoms include:
To diagnose EMP, doctors first need to rule out (exclude) several similar conditions — one in particular is multiple myeloma, the most common plasma cell neoplasm. Multiple myeloma is diagnosed by identifying the CRAB features:
These signs and symptoms are present in people with multiple myeloma but not in EMP. Although EMP and multiple myeloma are different conditions, some cases of EMP can progress to multiple myeloma, which is a more serious disease involving the whole body. However, EMP can be more easily cured.
People suspected of having EMP undergo blood and urine tests. A complete blood count is taken, which looks at red blood cells, white blood cells, and platelets, as well as markers of kidney function, abnormal proteins in the blood, and levels of calcium and other electrolytes. The urine is also tested for abnormal proteins.
EMP is characterized by a single tumor made of abnormal plasma cells. As part of the diagnosis process, a person may undergo a tissue biopsy of the suspect tumor. A sample of the tumor is taken and examined in a lab to confirm the presence of abnormal plasma cells. Additionally, to be diagnosed as EMP rather than solitary bone plasmacytoma, the tumor must be located outside of the bone, in the body’s soft tissue (for example, skin, muscle, tendons, nerves, and fat).
The absence of bone tumors or lesions can be confirmed by performing a skeletal survey, which uses X-rays to image all of the bones in the body at once, although MRI is now more commonly used. Computerized tomography (CT) scan or positron emission tomography (PET) combined with a CT scan may also be used to show the absence of bone tumors or damage.
Unlike people with multiple myeloma, those with EMP have normal bone marrow. To confirm a diagnosis of EMP and rule out multiple myeloma, there must be little (less than 5 percent) to no plasma cells in the bone marrow. This finding is confirmed by a bone marrow biopsy, during which a doctor extracts a sample of a person’s bone marrow and analyzes it for the presence of cancer cells.
Radiation therapy is the standard treatment for EMP. This is generally an effective treatment because EMP is highly sensitive to radiation and is isolated to only one part of the body. Success rates of radiation treatment are around 90 percent. Radiation can also help reduce the need for people with EMP to have painful and extensive surgeries to their head and neck region. However, when the spinal cord is affected, surgery may be required. Chemotherapy is not currently recommended as a first-line treatment for EMP.
The prognosis (or outlook) for EMP is generally favorable, with a five-year survival rate greater than 75 percent. EMP responds well to standard radiotherapy and surgery treatments. In about 10 percent to 30 percent of cases, EMP can develop into the more widespread disease, multiple myeloma. People who develop multiple myeloma will require additional follow-up care and treatment.
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