While its presentations and findings are similar to solitary plasmacytoma, solitary plasmacytoma with minimal bone marrow involvement is more likely to progress, i.e. it recurs or becomes overt multiple myeloma in 20% to 60% of cases within 3 years. Solitary plasmacytomas associated with 10% or more plasma cells are diagnosed as overt multiple myeloma. Non-secretory multiple myeloma
Non-secretory multiple myeloma represents a class of plasma cell dyscrasias where no myeloma protein is detected in serum or urine of patients with evidence of increased clonal bone marrow plasma cells and/or multiple plasmacytomas, particularly of the bone but also of soft tissues. While a pre-malignant phase is likely, most new cases of non-secretory multiple myeloma are brought to attention not because of incidental M protein detection which by definition is absent but because of patient symptoms indicative of malignancy possibly of plasma cell origin. The condition has been diagnosed based on biopsy-proved clonal plasma cell tumors and/or the presence in bone marrow of plasma cells at ≥10% of nucleated cells in individuals who have evidence of end organ damage attributable to an underlying plasma cell disorder. These patients typically also show one or more CRAB signs and lack evidence of a myeloma protein as measured by protein electrophoresis and immunofixation.
Its diagnoses must meet all four of the following criteria: biopsy-proven tumor consisting of clonal plasma cells; no evidence of any other plasmacytomas based on bone survey and MRI (or in place of MRI, CT scan); normal bone marrow examination; and absence end organ damage, CRAB features, or other signs or symptoms of systemic disease attributable to a plasma cell dyscrasia. Blood or urine myeloma proteins are usually undetectable or low in solitary plasmacytomas. Solitary plasmacytoma is a rare disease with an incidence in the USA of <450 cases per year. In a review of 1,691 cases in the US, the median age at diagnosis was 63 with males representing ~60% of all cases. The most common site of plasmacytoma involvement was bone (~58%) followed by upper or lower airway tract (~16%), soft tissue or connective tissue (~5%), central nervous system (~3%), gastrointestinal tract (~3%), skin (~1%), and all other sites (~3%). Overall median survival was 8.12 years with survival decreasing with age from 12.4 years for patients <40 to 5.2 years for patients of 60 years or older. Risk of its recurrence or progression to overt multiple myeloma within 3 years is ~10%.A subset of solitary plasmacytomas, termed solitary plasmacytoma with minimal bone marrow involvement, has the same criteria for diagnosis as solitary plasmacytoma except that bone marrow examination shows an increase in plasma cells from a normal value of ~0% to 1.5% to >~1.6% but less than 10% of total nucleated cells.