OBJECTIVETo study the characteristics histologic and cytologic features and clinical usefulness of plasma cell myeloma (PCM) subtyping according to WHO PCM classification.

METHODSBone marrow biopsy plastic-embedded sections were stained with H-G-E and Gomori's stains, and bone marrow aspirate smears were stained with Wright's stain. The clinicopathologic findings were then analyzed.

RESULTSOf the 131 cases with PCM, three types of growth patterns were noted: interstitial (21 cases, 16.0%), nodular (46 cases, 35.1%) and packed (64 cases, 48.9%). Besides, there were three cytologic subtypes: mature plasma cell type (43 cases, 32.8%), immature (81 cases, 61.8%) and pleomorphic (7 cases, 5.3%) types. The age of patients with mature plasma cell type was significantly higher than that of immature type (P = 0.005); and the number of tumour cells in bone marrow smears was significantly higher than that of immature type (P = 0.003). The numbers of WBC and platelets in peripheral blood were also significantly higher than that of pleomorphic type (P = 0.024, P = 0.002, respectively). On the other hand, the number of platelets in peripheral blood of immature type was significantly higher than that of pleomorphic type (P = 0.019). Marrow fibrosis was more frequently observed in immature type than in mature plasma cell type (P = 0.000). The incidence of marrow fibrosis and osteolytic lesions was higher in high risk group than in low risk group (P = 0.000, P = 0.023 respectively). Twenty-one cases (56.8%) of the 37 cases treated with MP or MP and M2 chemotherapeutic regimens showed good response. However, there was no significant difference in treatment response and survival between different subtypes.

CONCLUSIONSEach subtype of PCM carries different clinicopathologic features in some aspects. The classification carries important value in pathologic diagnosis and probably in predicting prognosis.