Azurophilic granules in myeloma cells

Clinical significance of granule-containing myeloma cells in patients with newly diagnosed multiple myeloma

The clinical features and prognostic significance of myeloma cells containing granules remain unclear. The purpose of this retrospective study was to investigate the clinical significance of granule-containing myeloma cells in patients with newly diagnosed multiple myeloma (NDMM). We retrospectively analyzed the records of 122 patients diagnosed with NDMM between January 2007 and December 2013. Granule-containing myeloma cells were defined as myeloma cells that exhibited three or more granules in their cytoplasm by May-Giemsa staining. The patients were classified into two groups, the granule-containing myeloma (GM) and nongranule-containing myeloma (non-GM) groups, depending on the proportion of myeloma cells that contained granules (cut-off value: 10%). There were 25 (20.5%) patients in the GM group. Patients in the GM group displayed significantly higher CD56 and CD49e expression than those in the non-GM group (t-test, P = 0.027 and 0.042). None of the patient characteristics differed significantly between the two groups. There was no significant difference in the chemotherapy profiles of the two groups, and the overall response rates of the two groups were similar. During the median follow-up period of 33.9 months, the overall survival (OS) in the GM group was similar to that in the non-GM group; 4-year OS of the GM and non-GM groups were 78.5% and 51.9%, respectively (P = 0.126). We concluded that cases of NDMM involving granule-containing myeloma cells are not infrequent. Moreover, CD56 and CD49e expression was significantly higher in the presence of myeloma cell populations, and the presence of granules did not affect survival.

Plasma cell morphology in multiple myeloma and related disorders

Normal and reactive plasma cells (PC) are easy to ascertain on human bone marrow films, due to their small mature-appearing nucleus and large cytoplasm, the latter usually deep blue after Giemsa staining. Cytoplasm is filled with long strands of rough endoplasmic reticulum and one large Golgi apparatus (paranuclear hof), demonstrating that PC are dedicated mainly to protein synthesis and excretion (immunoglobulin). Deregulation of the genome may induce clonal expansion of one PC that will lead to immunoglobulin overproduction and eventually to one among the so-called PC neoplasms. In multiple myeloma (MM), the number of PC is over 10% in most patients studied. Changes in the morphology of myeloma PC may be inconspicuous as compared to normal PC (30-50% patients). In other instances PC show one or several morphological changes. One is related to low amount of cytoplasm, defining lymphoplasmacytoid myeloma (10-15% patients). In other cases (40-50% patients), named immature myeloma cases, nuclear-cytoplasmic asynchrony is observed: presence of one nucleolus, finely dispersed chromatin and/or irregular nuclear contour contrast with a still large and blue (mature) cytoplasm. A peculiar morphological change, corresponding to the presence of very immature PC named plasmablasts, is observed in 10-15% cases. Several prognostic morphological classifications have been published, as mature myeloma is related to favorable outcome and immature myeloma, peculiarly plasmablastic myeloma, is related to dismal prognosis. However, such classifications are no longer included in current prognostic schemes. Changes related to the nucleus are very rare in monoclonal gammopathy of unknown significance (MGUS). In contrast, anomalies related to the cytoplasm of PC, including color (flaming cells), round inclusions (Mott cells, Russell bodies), Auer rod-like or crystalline inclusions, are reported in myeloma cases as well as in MGUS and at times in reactive disorders. They do not correspond to malignant changes of PC but are related to abnormal synthesis, trafficking, or excretion of the immunoglobulin that is stored in excess within the cytoplasm. Occurrence of crystalline inclusions within PC may be the first anomaly leading to the diagnosis of adult Fanconi syndrome. After a historical perspective, the authors report on the various morphological aspects of PC that may occur in multiple myeloma and related disorders, and discuss about their clinical and pathophysiological significance. Today, morphological identification and accurate determination of % PC within bone marrow remain ancillary criteria for the diagnosis of MM and help for the diagnosis of rare renal disorders.