|Ahead of print
Auer rod-like inclusions in multiple myeloma: Report of two diagnostically challenging cases
Arpita Mathur1, Shashi Bansal2, Upendra Sharma3, Amandeep Talwar1
1 Department of Pathology, Bhagwan Mahaveer Cancer Hospital and Research Centre, Jaipur, Rajasthan, India
2 Department of Pathology-Haematopathology, Bhagwan Mahaveer Cancer Hospital and Research Centre, Jaipur, Rajasthan, India
3 Department of Haemato-Oncology, Bhagwan Mahaveer Cancer Hospital and Research Centre, Jaipur, Rajasthan, India
|Date of Submission||06-Jul-2020|
|Date of Decision||02-Aug-2020|
|Date of Acceptance||29-Oct-2020|
|Date of Web Publication||19-Sep-2021|
Department of Pathology-Haematopathology, Bhagwan Mahaveer Cancer Hospital and Research Centre, Jaipur, Rajasthan
Source of Support: None, Conflict of Interest: None
Non-immunoglobulin intracytoplasmic inclusions in plasma cells of multiple myeloma are very rare presentation. These are morphologically similar to Auer rods but chemically different from them. We studied two cases of multiple myeloma in a 60-year-old woman and 45-year-old man. In both cases, plasma cells of bone marrow aspirate revealed multiple Auer rod-like inclusions (ARLI). Sudan black B (SBB) and myeloperoxidase (MPO) cytochemistry were negative. Serum protein electrophoresis in both of them showed M spike, one with raised IgA-kappa levels, while the other with raised IgG-kappa levels. Very few case reports have been published in the literature and its prognostic implications are still unknown. Due to its rarity, it is important to distinguish such cases from acute myeloid leukemia and its exact incidence with its therapeutic and prognostic implications.
Keywords: Auer rod-like inclusions (ARLI), cytochemistry, multiple myeloma, plasma cells
| » Introduction|| |
Presence of Auer rods More Details is a distinctive characteristic for diagnosis of acute myeloid leukemia (AML). Its composition was initially explained by Bainton et al. in 1977, who concluded that formation of Auer rods is result of defect in formation, aggregation and concentration of peroxide granules in leukemic blast. In recent years, few cases have been reported describing intracytoplasmic Auer rod-like inclusions (ARLI) in plasma cell dyscrasias like multiple myeloma (MM), monoclonal gammopathy of undetermined significance and plasma cell leukemia.,, Their presence in such type of non-leukemic cases has raised the need to study their composition and possible prognostic as well as therapeutic implications. Here, we present case report of two patients with MM demonstrating numerous intracytoplasmic ARLI, with morphology like faggot bodies in clonal plasma cells of bone marrow.
| » Case Report|| |
A 60-year-old woman referred to hematology clinic with 2-month history of body ache, weakness, difficulty in walking and anorexia. She was non-reactive for human immunodeficiency virus (HIV)/hepatitis B surface antigen (HBsAg)/hepatitis C virus (HCV), with no evidence of lymphadenopathy/organomegaly. She had normocytic normochromic anemia with mild thrombocytopenia–hemoglobin (Hb) 8.2 gm/dL (Reference range: 11.5 - 17.0 g/dL), total leukocyte count (TLC) 4.5 × 109/L (Reference range: 4.0 - 10.0 x109 /L), platelet count 146 × 109/L (Reference range: 150-410 x 109 /L) and markedly raised erythrocyte sedimentation rate (ESR) (130 mm at the end of first hour) (Reference range: ESR <19 mm at the end of first hour). Further investigations demonstrated mildly raised total proteins 8.34 gm/dL (Reference range: 6.4-8.3 gm/dL) with Albumin: Globulin ratio (A:G) 0.69 (Reference range: 1.1-2.2) and increased serum calcium 13.70 mg/dL (Reference range: 8.8-10.5 mg/dL). Bone marrow (BM) revealed suppression of normal hematopoietic tissue with presence of 29% plasma cells including mature and immature forms. Some of them had Auer rod-like needle-shaped crystalline intracytoplasmic inclusions. A few of them were arranged in bundles, thus mimicking faggot cells. These inclusions were myeloperoxidase (MPO) and Sudan black B (SBB) negative. Skeletal survey revealed multiple diffuse bony lytic lesions. Beta-2-microglobulin level was raised 11969 ng/mL (Reference range: 670-2143 ng/mL). Serum protein electrophoresis revealed two bands — band 1 (2.81 gm%) in beta-2 region and band 2 (0.33 gm%) in gamma region. Free kappa to lambda ratio was 635.56 (Reference range: 0.26-1.65). Thus, biclonal gammopathy was seen in IgA and kappa region and diagnosis of multiple myeloma international staging system (ISS) stage III was given. Immunophenotyping and cytogenetic studies were not performed due to financial restraints. The patient was started on intravenous hydration/injection zoledronic acid for hypercalcemia. VRD (combination of bortezomib, lenalidomide, and dexamethasone) chemotherapy regimen was started, and the patient received 2 weekly doses of injection bortizomib 2 mg/injection dexamethasone 40 mg along with daily lenalidomide 25 mg. Patient received chemotherapy for only 2 weeks and defaulted treatment and died within a year.
A 45-year-old man presented with 7-month history of back pain. He had history of falling on ground with difficulty in walking and standing. Subsequently, he developed paraplegia with bladder and bowel involvement. There was no history of oral mucosal lesions, and the patient was immunocompetent (non-reactive for HIV/HBsAg/HCV). On physical examination, no lymphadenopathy/organomegaly was noted. Routine investigations showed microcytic hypochromic anemia with leucopenia (Hb 8.7 gm/dL, TLC 2.8 × 109/L, platelets 251 × 109/L). Renal disease was evident with serum creatinine 1.53 mg/dL (Reference range: 0.52-1.25 mg/dL), serum urea 94.7 mg/dL (Reference range:15.0-45.0 mg/dL) and blood urea nitrogen (BUN) 37 mg/dL (Reference range: 7-20 mg/dL). Serum lactate dehydrogenase (LDH) was 238 U//L (Reference range: 140-280 U/L), and A:G 0.99. Initially, serum calcium was >16.5 mg/dL that was reduced to 11.5 mg/dL on administration of zoledronic acid after admission. On positron emission tomography–computed tomography (PET-CT), intense fluorodeoxyglucose (FDG) uptake was seen in collapsed D12 vertebra, showing diffuse lytic expansile lesion associated with bony destruction. Non-FDG multiple lytic punched out lesions were seen in calvarium, spine and bilateral iliac blades. No significant FDG avid lymphadenopathy/organomegaly or extramedullary lesions were noted on whole-body PET-CT scan. Biopsy from D12 vertebra exhibited sheets of monomorphic cells with eccentric nuclei, cartwheel chromatin and moderate cytoplasm. On immunohistochemistry (IHC), these cells were positive for CD20, CD138, CD56 and MUM1. Ki-67 proliferation index was 70%. Clonal nature was confirmed by kappa positivity and lambda negativity. In view of paraparesis and back pain, the patient received radiotherapy to D11 to L1 vertebra in dose of 30 Gy/15 fractions over 20 days. BM revealed 72% plasma cells on aspiration displaying pleomorphism with variable size, shape and nuclear maturation. Binucleate, trinucleate and multinucleate plasma cells, including a few giant forms were noted. Around 8-9% of plasma cells had plasmablastic morphology. Most of them showed intracytoplasmic ARLI with occasional faggot like cells. MPO was negative. Bone marrow biopsy showed bony trabeculae enclosing 8-9 intertrabecular marrow spaces. Most of the marrow spaces were markedly hypocellular with suppression of trilineage hematopoiesis. Only one space at the edge was hypercellular with marked suppression of normal hematopoietic tissue and was replaced by numerous plasma cells having binucleation, trinucleation and multinucleation [Figure 1]. Nuclear lobulations and mitotic figures were also evident which explained high Ki-67 on IHC. MM comprehensive panel revealed raised beta-2-microglobulin (11900 ng/ml) levels, M spike (0.60 g/dl) in gamma region and kappa to lambda ratio 14.70. Thus, it was interpreted as IgG-kappa monoclonal gammopathy. Flow cytometric immunophenotyping from BM revealed around 19-20% kappa restricted clonal plasma cells with lack of expression of CD19 and MPO. These cells showed bright expression of CD38 with heterogeneous expression of CD20, CD56 and CD117 [Figure 2]. Thus, MPO negativity was confirmed by dual methods, including cytochemistry and flow cytometry (FCM). Myeloma fluoroscent in situ hybridization (FISH) panel did not reveal any abnormality for deletion 13q, deletion 17p, monosomy 1/gain 1q, IGH gene re-arrangement, CCND1-IGH/t(11;14), FGFR3-IGH/t(4;14), IGH/MAFB/t(14;20) and IGH-MAF/t(14;16). In view of clinical history, BM findings, immunophenotyping, myeloma defining features with monoclonal M-band, the final diagnosis of anaplastic multiple myeloma (AMM), ISS stage III/revised ISS stage III with myeloma kidney and myeloma bone disease was kept. After stabilization of general condition, the patient was started on VCD regimen with injection bortezomib 1.3 mg/m2 weekly, tab lenalidomide dose adjusted to creatinine clearance, injection dexamethasone 40 mg weekly and injection zoledronic acid monthly. After receiving 2 weekly doses, the patient was lost to follow-up during COVID-19 lockdown in March 2020 and expired in April 2020.
|Figure 1: (a and b and inset) Bone marrow aspirate smears showing anaplastic plasma cells including bi- and trinucleated forms with bundles of Auer rod-like inclusions and faggot like bodies. (c) Myeloperoxidase stain negative plasma cells (internal control positive). Inset shows immature plasma cells with Auer rod-like inclusions. (d) H and E stained section from bone marrow biopsy reveals predominantly hypocellular marrow with only one marrow space at edge showing hypercellularity with suppression of normal hematopoetic tissue. Inset shows anaplastic plasma cells with nuclear lobulations and mitotic figures|
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|Figure 2: Antigen expression pattern in multiple myeloma. (a-c) Dot plots with statics reveal clonal plasma cells (dark blue), polymorphs (light blue), T-lymphoid cells (purple), B-Lymphoid cells (Red), Debris and Erythroid precursor (D/E-Brown). (d) Bright CD38 positive plasma cells with no expression of CD19. (e and f) KAPPA light chain restricted plasma cells with CD79a and MPO negativity. (g) Heterogeneous expression of CD117 and CD56 in clonal plasma cells|
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| » Discussion|| |
Although a few cases of ARLI in the plasma cells of MM have been published in literature, it is anticipated that without the aid of cytochemistry and immunophenotyping such cases could be misinterpreted as AML. Special stains like SBB and MPO that give positive staining for leukemic Auer rods are typically negative in MM. Justification for such difference can be explained by different chemical nature of both types of inclusions since Auer rods of myeloblasts are composed of MPO or chloroacetate esterase while inclusions of plasma cells are composed of plasma cell lysosomal enzymes like acid phosphatase, alpha-N-esterase or beta-glucuronidase. Moreover, ancillary techniques like IHC and FCM help resolve such diagnostic difficulties.
On reviewing the literature, it has been found that such type of intracytoplasmic inclusions is most commonly associated with IgG and kappa secreting myeloma.,,, This is a first case report that demonstrates association of ARLI with biclonal gammopathy. Only a few case reports on biclonal gammopathy are available in Indian medical literature. The incidence of double gammopathy among various cohorts of gammopathies in reported literature is 2–6%. Although clinical manifestations, treatment and response to therapy are similar to that of monoclonal gammopathy, the presence of ARLI with biclonal gammopathy is subject of importance as this phenomenon is unique and not reported till now.
Considering the aggressive nature with bizarre morphology of the second case along with high Ki-67 proliferation index, differential diagnosis of anaplastic/plasmablastic MM and plasmablastic lymphoma (PL) was debatable. Both are rare, aggressive and fatal disease with several overlapping morphologic and immunophenotypic features. PL most frequently presents as high-grade oral mucosal lesion in the setting of HIV infection, organ transplantation and advanced age. It is a rare B-cell neoplasm that arises from post-germinal centre, terminally differentiated, activated B cells. On immunophenotyping, it shows diffuse expression of markers of plasma cell differentiation like CD38, CD138, MUM1 and light chain restriction along with high Ki-67 proliferation index, while expression of CD56 and CD20 is characteristically absent. The distinction between PL and AMM is attributed to the correlation of clinical, radiological and laboratory features with the morphologic and immunophenotypic findings.
Another rarely encounter prototype of high-grade B-cell non-Hodgkins lymphoma (NHL) is diffuse large B-cell lymphoma with plasmacytoid differentiation (DLBCL-PD). This B lineage lymphoma has a cellular commitment to plasma cell program. Immunophenotypically, B cells with plasmablastic differentiation acquire the transcriptional and antigenic profile of plasma cells with a very high proliferation index. CD20 being one of the oldest B-cell lineage markers is positive in the majority of DLBCL. However, existence of a few CD20 negative DLBCL-PD is there. In such a scenario, an additional panel of CD19, CD79a, PAX5 and CD10 portray commitment to B-cell lymphoid lineage in DLBCL-PD. CD138 is universally accepted marker for normal and malignant plasma cells and express more significantly in B-cell marker negative lymphomas. Hereupon, combinations of plasma cell and extensive B-cell markers in the diagnostic algorithm are employed to define DLBCL-PD.
The factors that favored AMM include the presence of myeloma defining features (hypercalcemia, renal dysfunction, anemia, widespread bony lytic lesions), M-Band having monoclonal IgG-kappa, expression of CD38, CD138 along with presence of CD20, CD56 and CD117 on immunophenotyping. Absence of oral mucosal lesions/lymphadenopathy/hepatosplenomegaly in an immune-competent patient also contributed towards the diagnosis of myeloma. AMM is a rare and more aggressive subtype of MM with an aggressive clinical course and poor prognosis. It responds very little to conventional chemotherapy and optimal therapeutic strategy for AMM has yet to be established. Scant literature on AMM reveals that it can develop as de novo malignancy or progress from myeloma cells. We assume that presence of ARLI in association with the anaplastic morphology of plasma cells may point towards its aggressive behaviour.
There is lack of data depicting the molecular picture of such cases with ARLI. In the case report by Noujaim et al., FISH revealed monosomy 13 and possibly monosomy 14 or deletion of IGH sequence. Occurrence of cytogenetic abnormality is a frequent finding in multiple myeloma and these patients present at high ISS stage, relapse early and have poor prognosis. Both our patients presented at ISS stage III and died within one year of diagnosis. FISH studies were performed only in second case which doesn't reveal any cytogenetic abnormalities.
We extensively searched literature for prognostic significance of ARLI, but because of small number of observed cases, no organized studies were there. In 1998, Kurabayashi et al. studied ultrastructural abnormalities of plasma cells. They observed that a group of patients, having plasma cells with intracytoplasmic fibrillar formations had significantly shorter survival. In addition, an assumption has also been made regarding association of MM with ARLI and adult Fanconi syndrome.
| » Conclusion|| |
Only a few cases have been reported in the literature that tells us about the short survival of patients diagnosed with MM having ARLI. This is, however still an under-reported entity with unclear prognostic significance. The purpose of this case report is to make awareness about such an occurrence. These findings should be reported, so that these cases can be reviewed with respect to their stage, response to therapy, relapse rate and overall survival. Correlation of clinical, radiological and laboratory findings with IHC is crucial in establishing the correct diagnosis. This case highlights the importance of morphological evaluation (including vigilant search for intracytoplasmic inclusions) even in the era of modern molecular pathology.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
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Conflicts of interest
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