A retrospective study of correlation of morphologic patterns, MIB1 proliferation index, and survival analysis in 134 cases of plasmacytoma

Plasmacytoma classified into solitary plasmacytoma of bone (SPB) and extramedullary plasmacytoma (EMP) is characterized by infiltrate of plasma cells of diverse maturity and by their monoclonal immunoglobulin products. Both SPB and EMP represent different groups of neoplasm in terms of location, tumor progression, and overall survival rate. There is a need for features that indicate likelihood of myeloma in patients with plasmacytoma without other manifestations. This study was an attempt to study the morphologic patterns of plasmacytoma (SPB and EMP), MIB1 proliferation index, and correlation of these with clinicopathologic features and survival of the patients. The study group comprised of 134 cases of plasmacytoma (88 SPB and 46 EMP) over duration of 8 years and were graded as per Bartl's histologic grading system. Commonest site was vertebral body in SPB (36%) and upper aerodigestive tract in EMP (48%). On serum electrophoresis, overall M band was detected in 41% cases. Both SPB and EMP on histology revealed similar morphologic features. MIB1 proliferation index ranged from less than 1% to 80%. It was slightly higher in EMP in comparison with SPB (P value = .002). Seventy percent of cases, which progressed to multiple myeloma (MM) showed MIB1 labeling index more than 10%; however, it was not statistically significant in predicting the disease progression. With the median follow-up of 19 months (range, 1-99 months), 10 SPB had disease progression of which 7 converted to MM, and 3 developed EMP, with a median interval of 21 months (range, 8-75 months) for the development of MM and 3 months (range, 3-9 months) for the progression to EMP. Five-year survival for EMP varied by site, with poorest survival in brain/central nervous system EMP as compared with EMP at other sites. To conclude, grade and MIB1 proliferation index help in predicting aggressive course in plasmacytoma.