Patients and samples

We examined the samples collected from 110 patients diagnosed with MM between 2008 and 2010 at Asan Medical Center. The updated criteria for the diagnosis of MM were applied [37]. Cases without any available initial clinical information were excluded. Cases of localized plasma cell lesions without bone marrow involvement or biopsy specimens obtained at relapse were also excluded. Finally, a total of 81 bone marrow biopsy specimens were included in the analysis. Two expert hematopathologists verified the diagnosis of MM by reviewing the biopsy slides including special studies and clinical information. Clinical information was obtained from the medical records, including sex, age, immunoglobulin light and heavy chain restrictions, treatment details, presence of chromosomal abnormality, serologic markers, and 24h urine protein levels. Chromosomal abnormality was determined according to the results of cytogenetic studies which were composed of karyotype analysis and/or fluorescence in situ hybridization (FISH) analysis for IgH/FGFR3 rearrangement, IgH/CCND1 rearrangement, IgH/MAF rearrangement, 13q deletion, and TP53 deletion. Due to the retrospective nature of this study, the treatments differed among the cases. Of the treatments administered, ASCT and newer agents such as IMiDs (e.g., thalidomide and lenalidomide) and proteasome inhibitors (e.g., bortezomib) were selected as specific covariates. Conventional cytogenetic and/or FISH tests were performed for risk stratification. Durie Salmon (DS) stage, International Stage System (ISS), revised ISS (rISS), and the risk stratification used in the Mayo stratification algorithm (mSMART) [38] were applied for the classification of patients. The medical records were retrospectively reviewed and the clinical features, pathologic findings, cytogenetic results, and clinical outcomes of the patients were evaluated. To estimate the overall survival (OS) and event-free survival (EFS) rate, patients were followed from the date of diagnosis to the date of death. The cause of death was also recorded. To analyze the VSIG4 expression pattern in advanced stage of MM, extramedullary biopsy materials were also collected from 66 MM patients between 2000 and 2011 at the Asan Medical Center. For these patients, clinical information including age, sex, ISS, whether ASCT was performed, result of cytogenetics was also collected. The study protocol was approved by the Institutional Review Board (project number 2015-0751) of the Asan Medical Center.