Bone-marrow plasmocytosis--an immunohistological study

Mass spectrometric-based assessment of the serum kappa to lambda immunoglobulin light chain ratio (κ:λ) in dogs with immunoglobulin secretory diseases

The ratio of κ light chains to λ light chains (κ:λ) in serum is used as a biomarker of immunoglobulin secreting neoplasia in humans but has not been evaluated in dogs. A mass-spectrometry based method for determining the canine serum κ:λ was developed and used to evaluate samples from control dogs, dogs with an infectious aetiology, dogs with secretory plasma cell tumours (sPCT) and dogs with non-secretory B cell neoplasia. A human-targeted immunoturbidometric κ:λ assay and immunofixation using antisera targeting human κ light chain or λ light chain was also performed on all samples. Using whole serum samples, the MS-based κ:λ method identified 5 sPCT as κ-predominant (mean κ:λ = 3.307) and 5 sPCT as λ-predominant (mean κ:λ = 0.023) and documented differences between these groups and all other groups (p < 0.05 for all). The infectious aetiology group had a lower mean κ:λ ratio (mean κ:λ = 0.069) than control samples (mean κ:λ = 0.103, p = 0.035). Similar results were obtained when samples were enriched for proteins between 10 and 50 kDa using size exclusion chromatography, except for the statistical difference between the control and infectious aetiology group. All λ-predominant cases had only anti-human λ light chain labelling by immunofixation. Three κ-predominant cases had only anti-human κ-light chain labelling and the remaining two cases did not label with either antisera by immunofixation. The immunoturbidometric method had high analytical CV% (λ light chain CV = 13%, κ light chain CV = 50%), was unable to measure light chains in 20.5% of samples and did not distinguish groups. The data suggests that the human-targeted immunoturbidometric method would not be diagnostically useful and that the MS-derived serum κ:λ may be a useful biomarker of canine immunoglobulin secretory neoplasia which may have the ability to distinguish neoplasia from infectious causes of immunoglobulin secretion.

The cut-offs for kappa/lambda ratio in bone marrow immunohistochemistry for the diagnosis of multiple myeloma

Objective: The previously reported kappa/lambda ratio cut-offs for plasma cell clonality by immunohistochemistry were in different values. This study aimed to identify the cut-offs with the highest accuracy for the diagnosis of multiple myeloma. Methods: Bone marrow specimens consecutively recruited between January 2011 and March 2019. The patients were at least 18 years old with clinical suspicion of multiple myeloma and had bone marrow plasma cell ≥10% by CD138 immunohistochemistry. The index test was immunohistochemical stains for plasma cell kappa/lambda ratio. The reference standard to classify as multiple myeloma required meeting any of the following (1) kappa/lambda ratio ≤1/16 or ≥16, (2) abnormal plasma cell morphology, and (3) monoclonal immunoglobulin. Results: From 147 specimens (70 multiple myelomas and 77 reactive plasmacytosis), our cut-offs kappa/lambda ratio for light chain restriction at ≤1/7 or ≥9 yielded an area under the receiver operating characteristic curve of 1.0000 while ≤1/16 or ≥16 yielded 0.9643 (p-value 0.0212). Conclusion: The cut-offs for kappa/lambda ratio at ≤1/7 or ≥9 for diagnosis of multiple myeloma yielded the highest diagnostic accuracy. The suggested cut-offs could be of potential value in resource-limited laboratories.

Gastrointestinal bleeding as initial presentation of extramedullary plasma cell neoplasms: A case report and review of the literature

BACKGROUND

Plasma-cell neoplasms rarely involve the gastrointestinal tract and manifest as gastrointestinal bleeding. Plasmablastic myeloma is an aggressive plasma cell neoplasm associated with poor outcomes. A small number of cases with gastrointestinal involvement is reported in the literature and therefore high index of suspicion is essential for avoiding delays in diagnosis and treatment.

CASE SUMMARY

Our aim is to present our experience of a 70-year-old patient with a secondary presentation of plasmablastic myeloma manifesting as unstable upper gastrointestinal bleeding and to review the literature with the view to consolidate and discuss information about diagnosis and management of this rare entity. In addition to our case, a literature search (PubMed database) of case reports of extramedullary plasma cell neoplasms manifesting as upper gastrointestinal bleeding was performed. Twenty-seven cases of extramedullary plasmacytoma (EMP) involving the stomach and small bowel presenting with upper gastrointestinal bleeding were retrieved. The majority of patients were males (67%). The average age on diagnosis was 62.7 years. The most common site of presentation was the stomach (41%), followed by the duodenum (15%). The most common presenting complaint was melena (44%). In the majority of cases, the EMPs were a secondary manifestation (63%) at the background of multiple myeloma (26%), plasmablastic myeloma (7%) or high-grade plasma cell myeloma (4%). Oesophagogastroscopy was the main diagnostic modality and chemotherapy the preferred treatment option for secondary EMPs.

CONCLUSION

Despite their rare presentation, upper gastrointestinal EMPs should be considered in the differential diagnosis of patients with gastrointestinal bleeding especially in the presence of systemic haematological malignancy.

An approach for plasma cell myeloma diagnosis by two-color flow cytometry based on kappa/lambda ratios of CD38-gated plasma cells

Criteria from the World Health Organization (WHO) are commonly used to diagnose plasma cell myeloma (PCM), but they are complex and require several laboratory parameters. To differentiate reactive plasmacytosis from clonal plasma cell neoplasms, such as PCM, it is important to accurately determine the expression of the cytoplasmic immunoglobulin (cIg) light chain (LC). Through retrospective analyses, we selected the patients with PCM, and analyzed records of 52 PCM patients, who underwent bone biopsies, and final diagnosis of PCM was established according to WHO criteria, and 22 controls. In the present study, all samples were analyzed by flow cytometry (FC) in the side scatter vs CD38 histogram mode, and the CD38-gated plasma cell population was identified. The positive cell ratios of kappa and lambda to plasma cell populations were analyzed. PCM cells were distinguished from normal plasma cells by a cut-off level between 0.80 and 3.3, a sensitivity of 90.3 percent, and a specificity of 81.1 percent. Two-color FC analysis is simple to perform, inexpensive, and clinically relevant data are obtained soon after completion of the FC measurements. It could be one of the helpful tools in the diagnosis of PCM. The correct diagnosis of PCM can be achieved more simply, efficiently, and rapidly by combining this method.

An approach for diagnosing plasma cell myeloma by three-color flow cytometry based on kappa/lambda ratios of CD38-gated CD138(+) cells

BACKGROUND

World Health Organization (WHO) criteria are commonly used to diagnose plasma cell myeloma (PCM); however, these criteria are complex and require several laboratory parameters. For differentiating reactive plasmacytosis from clonal plasma cell (PC) neoplasms such as PCM, it is important to accurately determine the expression of cytoplasmic immunoglobulin light chains.

METHODS

We retrospectively analyzed the records of 27 selected patients with PCM who underwent bone biopsies for confirmative diagnosis according to WHO criteria. Twenty-three controls were also investigated. In the present study, all the samples were analyzed using flow cytometry (FC) in the side scatter vs. CD38 histogram mode, and the CD38-gated PC population was identified. Bivariate histograms of CD138/kappa and CD138/lambda were assessed, and the ratios of dual-positive cells to the CD138(+) PC population were calculated. The kappa/lambda ratio was defined as the ratio of CD138/kappa to CD138/lambda.

RESULTS

PCM cells were distinguished from normal PCs using cutoff levels between 0.76 and 1.5, at a sensitivity of 96.3% and specificity of 95.7%.

CONCLUSIONS

Three-color FC analysis is simple to perform and inexpensive, with clinically relevant data obtained soon after the completion of FC measurements. The detection of the cytoplasmic kappa/lambda ratio of CD38-gated CD138(+) PCs may be a useful tool in the diagnosis of PCM. To the best of our knowledge, this report represents the first diagnostic assessment of the cytoplasmic kappa/lambda ratio in CD38-gated CD138+ PCs using FC analysis. This method may help in more simple, efficient, rapid, and accurate diagnosis of PCM.

VIRTUAL SLIDES

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1568085959771735.

Bone marrow immunohistology of plasma cell neoplasms

The application of immunohistology to the spectrum of plasma cell disorders has yet to be incorporated widely into routine haematology practice. This technique enables the direct visualisation of specific surface and cytoplasmic antigens in the context of the individual cell and the surrounding anatomical neighbourhood. This review outlines the role of bone marrow immunohistology in the laboratory evaluation of patients with suspected and established plasma cell neoplasms and its emerging role in understanding myeloma biology for possible future therapeutic application.

Diagnostic criteria and histologic grading in multiple myeloma: histologic and immunohistologic analysis of 176 cases with clinical correlation

Diagnostic criteria in myeloma have not been completely standardized or tested for accuracy; furthermore, marrow findings of prognostic value have not been clearly identified. We studied 176 patients with myeloma to determine the relative value of marrow differential, tissue sections, and immunohistology singly or in concert in the diagnosis of myeloma and to correlate morphologic features with prognosis. Controls were patients with benign marrow plasmacytosis. Homogeneous nodules of plasma cells at least 1/2 high-power field and/or monotypic aggregates of plasma cells filling at least one interfatty marrow space correctly identified myeloma in 83.5% of cases, with no false positives. The current numerical criteria of marrow plasmacytosis > or = 10% occurred in 17.1% of the controls, and 39.7% of patients with myeloma had less than 10% marrow plasmacytosis at presentation. Myeloma was graded histologically into categories of none/minimal, moderate, and marked dysplasia on the basis of dysplastic features and mitoses; these categories correlated well with clinical outcome, with median length of survival of 32.9, 25.2, and 12.9 months, respectively (overall median length of survival of 123 patients with myeloma, 29.2 months). Packing of marrow by tumor and mitoses measuring at least 5/high-power field regardless of grade also was associated with a poor prognosis (median lengths of survival, 15.2 and 11 months, respectively). Myeloma may be diagnosed in the great majority of cases by demonstrating homogeneous nodules and/or monotypic aggregates of plasma cells in the marrow. Prognostic features were shown to include marked dysplasia, mitoses, packing of marrow by tumor, and clinical stage.

Immunoglobulin gene rearrangement in multiple myeloma: limitations of Southern blot analysis

Thirty-six patients with early and advanced multiple myeloma were investigated with Southern blot analysis to determine the presence of immunoglobulin gene rearrangement as evidence of clonality. Rearrangements were not uniformly found, being detected in only 14 of 19 patients with newly diagnosed myeloma and in 15 of 17 cases of clinically advanced myeloma. A correlation between percentage of bone marrow plasma cells and detection of immunoglobulin gene rearrangement was noted; however, in four cases of early myeloma with > 10% marrow plasma cells, no rearrangement was found. These results suggest that Southern blot analysis may not be an optimal method for the determination of clonality in plasma cell dyscrasias or, alternatively, that a proportion of the plasma cells found on bone marrow examination in some patients with early myeloma may not be monoclonal.

Differentiation of plasma cell infiltrates in the bone marrow. A clinicopathological study on 80 patients including immunohistochemistry and morphometry

In 80 patients immunohistochemical, morphometrical and clinical studies were performed on routinely referred trephine biopsies of the bone marrow showing an abnormal increase in plasma cells. From the approximately determined density of plasma cell infiltrates two main groups were distinguished, the first with an involvement exceeding 20% and the second with less than 10% of the total marrow area involved. The first group (n = 30; 324 +/- 130 plasma cells per square millimeter bone marrow) consisted of patients with frank malignant myeloma (MM) by clinical and histomorphological diagnosis. The second group (n = 50; 132 +/- 54 plasma cells per square millimeter bone marrow) with plasmacytic differentiation of infiltrates, had to be further divided into one component with evidence for initial or residual MM following chemotherapy (n = 27), another with obviously monoclonal gammopathy of undetermined significance--benign monoclonal gammopathy (BMG, n = 6), and a final set of cases with a reactive plasmacytosis mostly associated with an inflammatory condition (n = 17). There was an excellent agreement between the intracellular immunoglobulin staining as defined by the immunoperoxidase technique and the serum or urinary M-component detected by immunoelectrophoresis. In MM significant correlations were found between osteoclastic activity (number of osteoclasts specifically stained by acid phosphatase) per trabecular bone area, presence of lytic bone defects and the density of plasma cell infiltrates in the marrow. This latter feature corresponded well with the titer of secreted serum M-components measured by quantitative immunoelectrophoresis. Using morphological data alone, BMG cases could not be discriminated with any certainty from initial or residual plasmacytic MM. They consequently need a prolonged clinical follow up to clarify the nature of the lesions.