Background: The relationship between solitary plasmacytoma and multiple myeloma is still unclear, but they can be distinguished by their different clinical course. Indicators of disease activity and extension, and of a possible evolution to multiple myeloma, have not been identified as yet.
Methods: Two cases of solitary plasmacytoma are described: one of the mandible and one extramedullary plasmacytoma (EMP) of the rhinopharynx. Pathologic data included immunohistochemical staining for heavy and light Ig chains, and for the proliferating cell nuclear antigen (PCNA). Analysis of the peripheral immunological status and serum parameters (beta 2 microglobulin, thymidine kinase, IL-2, IL-6 and soluble IL-2 receptor) was performed and correlation was made with the clinical status. Flow cytometry analysis of nuclear DNA content and S-phase cell fraction were also studied in both neoplasms.
Results: Solitary plasmacytoma of bone (SPB) showed important basal immunologic alterations and a marked increase in all serum parameters considered with respect to EMP. Ploidy analysis demonstrated an almost complete aneuploidy cell population for the SPB patient (80%), whereas in the EMP patient only 2% of the cells were aneuploid. The S-phase cells were 16% and 4%, respectively. PCNA index was 60% in SPB and 10% in EMP.
Conclusions: Solitary plasmacytoma of the bone appeared to be a more aggressive form of plasmacellular neoplasia, distinct from EMP and similar to multiple myeloma. The study of serum parameters, together with analysis of PCNA, ploidy and S-phase fraction, can aid in better understanding disease activity, and in the choice of more adequate treatment. Moreover, serial analysis of some serum factors might be useful markers for monitoring the disease.