Auer‐rod like inclusions in multiple myeloma

Abstract

A variety of types of inclusions are seen in the neoplastic cells of multiple myeloma (plasma cell myeloma). Among these, crystalline inclusions resembling Auer rods are uncommon. This 47-year-old Iraqi woman presented with back pain and anemia (haemoglobin concentration 100 g/l). A diagnosis of immunoglobulin (Ig) Gj myeloma with Bence-Jones proteinuria was made [1]. The bone marrow was heavily infiltrated by cytologically abnormal plasma cells including multinucleated and nucleolated cells (left). In addition the majority of neoplastic cells contained azurophilic cytoplasmic crystals. A further curious feature (right) was the presence of mitotic figures within crystal-containing myeloma cells, the presence of the crystals serving to identify the cells in mitosis as myeloma cells.Auer-rod like inclusions in myeloma cells have been described in association with IgG, IgA, IgM and light chain only (kappa) myeloma[2]. They are generally[2], but not invariably [3], associated with paraproteins with kappa light chains and are more often associated with IgA myeloma. They do not represent immunoglobulin but rather are of lysosomal origin, being positive for alpha naphthyl acetate esterase, beta glucuronidase and acid phosphatase [4]. There is an association with adult Fanconi syndrome due to deposition of crystals in renal tubules [2]. Myeloma cells can also contain crystalline inclusions that do represent immunoglobulin but these differ from Auer-rod like inclusions in that they stain pale pink on Romanowsky stains, rather than being azurophilic.

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

“…The cells stained positive by EST in four of nine cases and none were positive in MPO or PAS staining. There are other reports, which demonstrated that Auer rod-like inclusions were detected in cytoplasm of myeloma cells [25][26][27][28][29][30][31]. We considered that the inclusions in the cells of the GM group were not identifiable with Auer-like rods, because the shape of inclusions in the GM cells was quite different from that of Auer-like rods.…”

White rodlike crystals in multiple myeloma cells

“…Steinmann was also the first time to prove that these inclusions to be of lysosomal origin (fusionated lysosomal granules). Following that report, many more cases have been described [1,2,[4][5][6][7][8][9][10]. Pooling together all the cases reviewed by Hütter [1] and other reports, including our cases, it appears that this phenomenon is always associated with a IgG κ-type paraprotein, only two cases of λ light chain restriction [4][5][6][7][8][9][10][11][12][13][14].…”

“…Pooling together all the cases reviewed by Hütter [1] and other reports, including our cases, it appears that this phenomenon is always associated with a IgG κ-type paraprotein, only two cases of λ light chain restriction [4][5][6][7][8][9][10][11][12][13][14]. Although plasma cell myeloma with these inclusion bodies has been considered to be a morphologic variant and has intrigued investigators, the prognostic value is still unclear [9][10][11][12][13][14]. Additionally, there is still no known cytogenetic association nor any particular immunophenotypic characteristic relationship.…”

Azurophilic granules in myeloma cells

“…In this patient with immunoglobulin G kappa myeloma a large proportion of the myeloma cells contained azurophilic granules, sometimes round and sometimes irregular (image). By analogy with the azurophilic Auer rod‐like inclusions with similar staining characteristics that may be observed in myeloma , it is likely that these inclusions are of lysosomal origin. In one reported case, the granules were positive for acid phosphatase and weakly positive for alpha naphthyl butyrate esterase; on ultrastructural examination they were distinct from the endoplasmic reticulum and were considered likely to be vacuoles of the lysosomal system .…”