The neoplastic cells of multiple myeloma (plasma cell myeloma) show a wide range of cytological abnormalities. These include cytoplasmic inclusions composed of immunoglobulin, which may be either crystalline or globular, the latter either clearly in the cytoplasm (Russell bodies) or invaginated into the nucleus (Dutcher bodies). A distinctive type of rod-shaped azurophilic inclusion does not represent immunoglobulin but rather is lysosomal in origin [1].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 [1,2], 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 [3]. Azurophilic cytoplasmic granules have been observed in association with both kappa [4] and lambda [3] light chains.
A 60-year-old male was referred with a four month history of anemia and persistent chest infections. His blood count showed hemoglobin concentration 76 g/l, MCV 93.2 fl, neutrophils 1.8 × 10 9 /l and platelets 247 × 10 9 /l. A blood film showed anisopoikilocytosis, basophilic stippling, hypogranular neutrophils, and occasional pseudo-Pelger-Huët forms. No blast cells were seen. Serum vitamin B 12 was normal at 196 ng/l (normal range 160−800), although the serum folate was slightly below normal at 101 ng/ml (126−480 ng/ml).A bone marrow aspirate was hypercellular. Erythropoiesis was markedly increased at 79% and myelopoiesis was markedly reduced. Myeloblasts were not significantly increased at 3%. There was gross dyserythropoiesis with multinucleated and giant erythroblasts being prominent (images); there were up to five nuclei per erythroblast and nuclei of a single cell sometimes differed in size and chromatin structure. Other erythroid abnormalities included nuclear fragmentation, internuclear bridges, prominent nucleoli (centre), cytoplasmic vacuolation (centre), and basophilic stippling. Most erythroblasts were normoblastic with a minority being megaloblastic. Some of the erythroblasts were reminiscent of those in congenital dyserythropoietic anemia but the presence of neutrophil dysplasia pointed to a diagnosis of myelodysplastic syndrome.The suspicion of a haematological neoplasm was confirmed by cytogenetic analysis. This revealed a complex male karyotype in seven of the ten metaphases analysed. A single near diploid cell showed monosomy 5 and 12, additional material replacing the short arm of chromosome 21 and a marker chromosome of unknown origin. The remaining six abnormal cells showed a hypotetraploid karyotype. The abnormalities appeared to have arisen from a genome doubling event affecting an abnormal clone represented by the single near-diploid cell, with subsequent loss of chromosome 8, 9, 11, 14, 15 and 18. The abnormalities were variable between cells. The composite karyotype was 45,XY,-5,-12,add(21 -3,-3,-5,-5,-7,-7,-8,-9,-11,-12,-12,-15,-16,-16,-17,-17,-18,add(21) The final diagnosis was refractory anemia with multlineage dysplasia (myelodysplastic syndrome with multilineage dysplasia in the 2017 revision of the WHO classification).
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