Solitary plasmacytoma and multiple myeloma are types of cancer that form from plasma cells. Plasma cells are white blood cells that work as part of the immune system. Normally, these cells produce antibodies, which are proteins that help recognize and fight infection. However, genetic defects can occur that cause plasma cells to multiply uncontrollably, giving rise to a group of diseases known as plasma cell neoplasms (plasma cell cancers) such as solitary plasmacytoma and multiple myeloma.

Solitary plasmacytoma and multiple myeloma are rare diseases and have several distinguishing features.

What Is Multiple Myeloma?

Multiple myeloma is the most common plasma cell cancer. It forms when abnormal plasma cells form tumors in the bone marrow. The cancer cells make an abnormally large amount of an antibody called monoclonal immunoglobulin or M protein, which can’t fight infection properly. M protein then accumulates in the body.

Multiple myeloma is a rare disease overall, accounting for about 1 percent of all cancer cases with approximately 30,000 cases per year.

What Is Solitary Plasmacytoma?

Solitary plasmacytoma is also formed from abnormal plasma cells. Unlike multiple myeloma, however, solitary plasmacytoma is characterized by a plasma cell tumor that grows in a single location rather than in multiple bone marrow sites throughout the body. The most common location of the tumor is bone, and solitary plasmacytoma is often called solitary plasmacytoma of bone. It is a much rarer disease than multiple myeloma, with fewer than 450 cases per year.

Symptoms of Solitary Plasmacytoma vs. Multiple Myeloma

Common signs of multiple myeloma are often referred to using the abbreviation CRAB, which stands for:

• Calcium in high levels
• Renal (kidney) failure
• Anemia (low red blood cell count)
• Bone lesions (tumors)

Other signs and symptoms of multiple myeloma include:

• Bone pain or fractures
• Fatigue
• Frequent infections

In contrast to multiple myeloma, solitary plasmacytoma does not cause CRAB symptoms. Solitary plasmacytoma has overall fewer symptoms, which may include:

• Bone pain
• Sensory and movement defects, in cases when the spinal cord is affected

Diagnosis of Solitary Plasmacytoma vs. Multiple Myeloma

To diagnose multiple myeloma or solitary plasmacytoma, doctors perform a series of laboratory tests to look for features of the disease.

Tests for Multiple Myeloma

Your doctor may use different tests to look for the signs and symptoms of multiple myeloma.

CRAB Criteria

High levels of calcium, renal failure, and anemia can be determined using a blood test or urine test. The presence of bony lesions can be confirmed using imaging techniques such as X-ray, computerized tomography (CT) scan, or positron emission tomography (PET) combined with a CT scan.

M Protein Levels

Multiple myeloma and plasmacytoma often cause high levels of an antibody referred to as M protein. Accumulation of M protein can be detected using a blood test.

Cancer Cells in Bone Marrow

Finding that abnormal plasma cells make up at least 10 percent of cells in the bone marrow can lead to a diagnosis of multiple myeloma. To make this determination, your doctor may do a bone marrow biopsy, in which they obtain and analyze a bone marrow sample.

Tests for Solitary Plasmacytoma

To distinguish solitary plasmacytoma from multiple myeloma, the doctor must confirm abnormal bone marrow and the absence of CRAB symptoms. Doctors must also examine a person for additional evidence of disease. For instance, a single tumor, generally in the bone, must be observed to confirm diagnosis of solitary plasmacytoma. Bone lesions are detected using X-ray, CT, or PET imaging technologies.

Treatment Options for Solitary Plasmacytoma vs. Multiple Myeloma

The treatment options for the two conditions differ.

Treatment for Multiple Myeloma

There are several options for treating multiple myeloma. The exact treatment recommended by a doctor depends on individual factors such as your age and stage of the disease.

Chemotherapy

Initial treatment of multiple myeloma generally involves chemotherapy to kill cancer cells. There are several chemotherapy drugs approved to treat multiple myeloma, and these regimens generally include combinations of different drugs, such as Velcade (bortezomib) and Cytoxan (cyclophosphamide).

Other Drug Therapy

In addition to chemotherapeutic drugs, other types of drugs are often used to treat multiple myeloma. These drugs include immunomodulators such as Revlimid (lenalidomide), which are drugs that affect how the immune system works. Corticosteroid drugs might also be prescribed, often in combination with chemotherapy.

Stem Cell Transplant

Also called a bone marrow transplant, a stem cell transplant when used for myeloma treatment involves replacing the cells in a person’s bone marrow with healthy cells after high doses of the chemotherapy drug Melphalan destroy the bone marrow (and any myeloma living there). There are two types of stem cell transplants. An autologous stem cell transplant, which is more commonly recommended, means the stem cells come from the person’s body. The other option is an allogeneic stem cell transplant, in which stem cells come from a donor. Allogeneic stem cell transplant is rarely used to treat myeloma.

Treatment for Solitary Plasmacytoma

Radiation therapy is the standard treatment for solitary plasmacytoma. Because only a single tumor is involved, radiation is generally effective at treating the disease. Surgery may also be recommended in some cases.

Outlook for Solitary Plasmacytoma vs. Multiple Myeloma

The five-year survival rate for solitary plasmacytoma is as high as 70 percent, although it can vary depending on the location of the tumor and the type of treatment received. Solitary plasmacytoma is potentially curable with standard treatments, but solitary plasmacytoma can develop into multiple myeloma. In those cases, a person affected would require additional treatment.

Relative to solitary plasmacytoma, multiple myeloma has an overall worse prognosis (outlook). After initial treatment success, most patients relapse, and cancer will reappear after time. The five-year survival rate is approximately 50 percent. Newer, more effective treatments are being developed to improve the prognosis for people diagnosed with multiple myeloma.

Talk With Others Who Understand

MyMyelomaTeam is the social network for people with multiple myeloma. On MyMyelomaTeam, more than 13,000 members come together to ask questions, give advice, and share their stories with others who understand life with myeloma.

Are you living with multiple myeloma or solitary plasmacytoma? Share your experiences in the comments below, or start a conversation by posting on your Activities page.