Myeloma is a type of cancer. It occurs when the plasma cells (type of white blood cells) become malignant or cancerous. Plasma cells are also called B Lymphocytes and they are responsible for producing antibodies.
Like all blood cells, plasma cells are produced in the bone marrow and myeloma occurs mainly in the bone marrow of large bones. Eventually the myeloma cells break out and invade the bone causing 'osteomyeloma' - osteo=bone.
Myeloma cells also spread to other organs and parts of the body leading to 'multiple myeloma'