Fig. 1

Bone marrow (BM) aspirate smear showed primitive and immature mononuclear cells (a: original magnification × 100 under oil) and abnormal plasma cell morphology (b: original magnification × 100 under oil). BM trephine biopsy showed increased hyperplasia activity (70 %), widely distributed naive cells, large cell body, abundant cytoplasm, and several irregular nuclei with prominent nucleoli. The percentage of plasma cells increased, and the cells featured special-shaped scattered or clustered distribution with positively stained reticular fibers (c: original magnification × 100 under oil). d: Flow cytometric immunophenotyping of abnormal plasma cells showed positive CD138, CD38, CD56 and λ expression, and negative CD19 and CD45 expression. e: The phenotypic characteristics of malignant myleoid cells showed strong positive CD38 expression, positive CD117, CD34, CD33, HLA-DR, CD56, CD13, and MPO expression, and negative CD5, CD11, CD64, CD20, and CD70 expression. f: The gene expression of RB-1, IgH, TP53, and CDKN2C/CKS1B as indicated by the results of FISN analysis on immunomagnetically separated abnormal plasma cells. Note: A-1, B-1, C-1, and D-1 for normal bone marrow cells; A-2, B-2, C-2, and D-2 for the patient’s bone marrow cells. Testing of RB-1 (13q14) by using Vysis and monochrome-labeled probe showed normal 2R signal (A-1) and positive 1R signal characteristics (A-2) (fusion signal showing red color). Testing of IgH (14q32) by using Vysis and dual-color separately labeled probe (signal: green for 5′ IgH and red for 3′ IgH) showed fusion signal with yellow color or green–red overlying color, which represented normal expression of IgH in B-1 and B-2. Testing of TP53 (17p13) by using Vysis and monochrome-labeled probe showed normal 2R signal (C-1) and positive 1R signal characteristics (C-2) (fusion signal showing red color). Testing of CDKN2C (1p32)/CKS1B (1q21) by using Vysis and dual-color separately labeled CKS1B/CDKN2C probe (signal: green for CDKN2C and red for CKS1B) showed normal 2R2G signal and characteristics in D-1 and positive signal for 3R2G 1q21 amplification and 2R1G deletion of 1p32 in D-2