• Solitary osseous plasmacytoma (solitary myeloma of bone) means there is a single plasma cell tumor in the 
  bone. X-rays of the bones show no other lytic lesions and the bone marrow is normal. About 25 percent of 
  patients will have an M-protein in the serum or urine. Patients found to have a solitary lytic bone lesion with 
  conventional x-rays should also be examined by magnetic resonance imaging (MRI). MRI can detect bone l
  lesions that cannot be seen with conventional x-rays. This tumor should be treated with high doses of
  radiation to the lesion, but about 60 percent of patients will develop multiple myeloma within 10 years.
• Extramedullary plasmacytoma is a tumor consisting of myeloma cells but occurs outside the bone marrow.
  The most commonly involved area is the back of the nose and throat (nasopharynx), and the sinuses may also
  be involved. Eighty percent of cases involve the upper respiratory area.
      Extramedullary plasmacytomas may also involve the stomach, small bowel, colon, urinary bladder, thyroid,
  breast or the brain. Examination of the bone marrow is normal, and the patients have no lytic bone lesions. If
  an abnormal protein is present, it should disappear after treatment. Diagnosis of a plasmacytoma is made after
  a biopsy of the tumor. It is treated with radiation therapy . Most patients are cured, but the disease may recur
  in a nearby area. The development of typical multiple myeloma is uncommon.

What Causes It  The cause is not known. Detailed studies of the atomic bomb survivors in Japan have not revealed an increased incidence of myeloma. There is little evidence that exposure to chemicals or electromagnetic fields causes myeloma.