OBJECTIVETo analyze the clinical and laboratory features and risk factors of multiple myeloma (MM) with extramedullary disease (EM) and its extraosseous localizations at diagnosis and during the course of MM.

METHODSThe clinical features, survival rate and prognostic factors were retrospectively analyzed in 40 patients having EM from a total of 418 MM patients hospitalized in Changzheng Hospital from 1993 to 2006.

RESULTSAmong the 40 patients, the first three localizations of EM involved soft tissue, pleura or peritoneum and central nervous system (CNS). Median duration of follow-up was 30 months. The median overall survival (OS) was 28 months. Twenty-five patients (6%) were found to have EM at diagnosis (group A), and their median OS was 16 months and 15 patients (3.6%) developed EM during the course of the disease (group B), and their expected median OS was 72 months. There was a significant difference between group A and B (P = 0.0045) for OS. Compared with those in group A, patients in group B had a higher percentage of plasmacytes (P = 0.022) and plasmablasts (P = 0.029) in bone marrow, and less advanced stage for international staging system (ISS) (P = 0.027). Log-rank univariate analysis showed that higher CRP level, higher serum LDH, Stage II and III for ISS, Hb < 110 g/L at diagnosis were poor prognostic factors. However, multivariate analysis with COX model showed none of them were statistically significant.

CONCLUSIONEM tumors are not a rare manifestation of MM. Soft tissue in the commonest area involved. Higher serum CRP and LDH level, more advanced stage for ISS, anemia and having EM are poor prognostic factors of MM.