OBJECTIVETo explore the morphological characteristics of bone marrow cells of multiple myeloma with non-bone-related extramedullary disease and thier clinical significance.

METHODSBone marrow smears, peripheral blood smears and bone marrow biopsy sections as well as thier examination results of 20 cases of multiple myloma with non-bone-related extramedullary disease were collected at initial diagnosis in First Affiliated Hospital of Xi'an Jiaotong University from March 2013 to March 2016, and morphological characterisistes of bone marrow cells were analysed in combination with clinical data.

RESULTSThe morphology of plasma cells in 20 patients showed 2 cytologic subtypes: primitive cell type (16 cases) and pleomorphic type (4 cases). Immature plasma cells were found in the 5 patients' peripheral blood smear, accounting for about 1%-4% of the number of peripheral blood cells. In bone marrow tissue, plasma cells hyperproliferated with nodular and packed type, and secondary myelofibrosis counted for 12 cases (60%). 13 MM patients whose non-bone-related extramedullary disease occurred during therapy were divided into 2 groups according to the marrow fibrosis density. The median time from diagnosis of MM to extramedullary lesions resulting from fibrosis 0-1 grade and 2-3 grade was 23.7±3.7 months and 10.5±3.2 months ahead of the former(P=0.025).

CONCLUSIONBone marrow plasma cell morphology of multiple myeloma with non-bone-related extramedullary disease at the initial diagnosis is mostly immature type, and plasma cells proliferate with nodular and packed type and accompanied by different degree of fibrosis. The degree of myelofibrosis indirectly reflects the degree of proliferation and malignancy of the bone marrow plasma cells, which maybe possess some value in predicting extramedullary disease in the early stages of the MM.