Objective: To study the characteristics histologic and cytologic features and clinical usefulness of plasma cell myeloma (PCM) subtyping according to WHO PCM classification.
Methods: Bone 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.
Results: Of 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.
Conclusions: Each subtype of PCM carries different clinicopathologic features in some aspects. The classification carries important value in pathologic diagnosis and probably in predicting prognosis.