Interphase FISH in plasma cell dyscrasia: increase in abnormality detection with plasma cell enrichment

A Comprehensive Review of the Genomics of Multiple Myeloma: Evolutionary Trajectories, Gene Expression Profiling, and Emerging Therapeutics

Multiple myeloma (MM) is a blood cancer characterized by the accumulation of malignant monoclonal plasma cells in the bone marrow. It develops through a series of premalignant plasma cell dyscrasia stages, most notable of which is the Monoclonal Gammopathy of Undetermined Significance (MGUS). Significant advances have been achieved in uncovering the genomic aberrancies underlying the pathogenesis of MGUS-MM. In this review, we discuss in-depth the genomic evolution of MM and focus on the prognostic implications of the accompanied molecular and cytogenetic aberrations. We also dive into the latest investigatory techniques used for the diagnoses and risk stratification of MM patients.

Utility of Flow Cytometry and Fluorescence In Situ Hybridization in Follow-up Monitoring of Plasma Cell Myeloma

OBJECTIVES

We sought to investigate the clinical utility of flow cytometry (FC) and fluorescence in situ hybridization (FISH) in the workup of myeloma.

METHODS

We retrospectively reviewed the reports of bone marrow biopsies received for myeloma evaluation between October 2015 and January 2019.

RESULTS

A total of 1,708 biopsy specimens from 469 myeloma patients (mean age, 64.5 years [SD, 9.3]; female, 41.4%) were reviewed. Both FC and FISH had comparable detection rates at the time of initial diagnosis (97.6% vs 98.8%) and for follow-up cases (28.6% vs 28.2%). FC and FISH results were concordant in 98.8% of the initial diagnosis cases and 89.6% of the follow-up cases. The FISH-positive (FISH+)/FC-negative (FC-) discordance and FISH-/FC+ discordance occurred among 81 (5.0%) and 87 (5.4%) follow-up cases. In comparison with all concordant cases, FISH+/FC- discordant cases were more likely to have received treatment with daratumumab (P < .05).

CONCLUSIONS

Plasma cell-enriched FISH and FC have comparable abnormal plasma cell detection rates, and approximately 10% of the follow-up cases have discordant FISH and FC results in which residual disease is detected by only one of these modalities. FISH testing should be considered for cases with negative FC, especially in patients who have received treatment with daratumumab or in cases in which there is concern about specimen adequacy.

Risk Stratification in Multiple Myeloma in Indian Settings

Multiple myeloma (MM) constitutes 10% of all hematological malignancies. The last one decade has seen a phenomenal progress in the therapeutic options available for the management. Although it still remains incurable, with the advent of newer therapies, the median survival in many risk groups is now around 10 years. Conventional karyotyping of bone marrow samples has a positivity rate of 20-30% at diagnosis in patients of Multiple Myeloma. However, array Comparative Genomic Hybridisation (aCGH) has revealed that almost all MM patients have cytogenetic abnormalities which may affect the pathophysiology, selection of therapy and outcomes of the disease. The progress in the field of exploring the genetic landscape of multiple myeloma with multiple tools like Fluorescent in-situ hybridization, aCGH, Next Generation Sequencing, Flow cytometry, etc., combined with the traditional risk stratification markers like albumin, β2 microglobulin and LDH, is gradually leading towards a risk-adapted therapy. The recent R-ISS risk stratification has combined these two group of information to validate a prognostic score which is an improvement over the past tools like DSS and ISS. In view of the plethora of information available on the multitude of cytogenetic markers there is a tendency to evaluate for all of them at diagnosis, especially in research centers. This leads to a significant increase in the cost of therapy of Multiple Myeloma in day-to-day clinical practice and an increased out-of-pocket spending to the patient, especially in resource-limited settings like India. Also, there is a variable approach to pre-therapy cytogenetic evaluation and risk stratification at different Hematology centres in the country, often dictated by financial constraints and availability of specialized tests. This review discusses the risk stratification markers and tools available in MM in 2019 and how it can be adapted in the resource constraint settings so as to derive the maximum prognostic information from a minimal prognostic panel, as well as lead to standardization of the prognostic protocols in resource limited settings across various Hematology centres in India.

Optimal strategy for obtaining routine chromosome analysis by using negative fractions of CD138 enriched plasma cells

Fluorescence in situ hybridization (FISH) is superior to routine chromosome analysis (RCA) in detecting important prognostic genetic abnormalities in plasma cell dyscrasia (PCD); however, its sensitivity is hampered due to paucity of plasma cells (PC) in whole bone marrow (BM). Studies showed that the abnormality detection rate in enriched plasma cells (EPC) is greater than unselected plasma cells (UPC), but purification techniques are limiting to only FISH when sample volumes are inadequate. Not performing RCA may compromise patient care since RCA is equally important for detecting non-PC related abnormalities when the diagnosis is undefined. To resolve this critical issue, we designed a study where an immuno-magnetic CD138 enriched positive selection was used for FISH while the negative fraction (NF) was used to retrieve other myeloid elements for RCA. Parallel FISH studies were performed using UPC and CD138 EPC, while karyotyping was achieved using whole BM and discarded myeloid elements from the NF. Results showed that the abnormality rate of EPC was doubled compared to UPC for FISH, and CA displayed 100% success rate using the NF. PCD related chromosome abnormalities were confined to whole BM while non-PCD related abnormalities were found in both whole BM and NF. Our results demonstrate the feasibility of using the NF for RCA.

Plasma cell enrichment enhances detection of high-risk cytogenomic abnormalities by fluorescence in situ hybridization and improves risk stratification of patients with plasma cell neoplasms

CONTEXT

Methods for plasma cell enrichment of bone marrow (BM) specimens can increase the sensitivity of fluorescence in situ hybridization (FISH) for detecting cytogenomic abnormalities. There are no published reports using these methods to evaluate high-risk cytogenomic abnormalities in patients with plasma cell neoplasms (PCNs) after therapy.

OBJECTIVE

To evaluate the utility of plasma cell enrichment combined with FISH for detection of high-risk cytogenomic abnormalities in patients with PCNs after therapy.

DESIGN

Twenty-eight patients with PCNs, of whom 22 received treatment, were included in this study. Plasma cells were enriched in BM aspirates by using a magnetic cell-sorting procedure to select CD138(+) cells. Probes were chosen to assess for del(17p13/TP53), del(13q14/RB1), 1q21/CKS1B gain, IgH/FGFR3, and IgH/MAF. Clinicopathologic data were collected during clinical follow-up after plasma cell enrichment.

RESULTS

Plasma cells in nonenriched BM specimens ranged from 1% to 28% (median, 8%) compared with 28% to 96% (median, 73%) in enriched BM specimens (P < .001). In a subset of treated patients in clinical remission, FISH detected high-risk cytogenomic abnormalities only in plasma cell-enriched samples. This approach also detected abnormalities in cases of solitary plasmacytoma and monoclonal gammopathy of undetermined significance.

CONCLUSIONS

Plasma cell enrichment of BM specimens increases FISH sensitivity for detecting high-risk cytogenomic abnormalities, particularly in treated patients, and these results, in combination with clinical follow-up data, can be of value to improve risk stratification and patient management.

Array-based karyotyping in plasma cell neoplasia after plasma cell enrichment increases detection of genomic aberrations

The discovery of genomic abnormalities present in monoclonal plasma cells has diagnostic, prognostic, and disease-monitoring implications in plasma cell neoplasms (PCNs). However, technical and disease-related limitations hamper the detection of these abnormalities using cytogenetic analysis or fluorescence in situ hybridization (FISH). In this study, 28 bone marrow specimens with known PCNs were examined for the presence of genomic abnormalities using microarray analysis after plasma cell enrichment. Cytogenetic analysis was performed on 15 of 28 samples, revealing disease-related genomic aberrations in only 3 (20%) of 15 cases. FISH analysis was performed on enriched plasma cells and detected aberrations in 84.6% of specimens while array comparative genomic hybridization (aCGH) detected abnormalities in 89.3% of cases. Furthermore, aCGH revealed additional abnormalities in 24 cases compared with FISH alone. We conclude that aCGH after plasma cell enrichment, in combination with FISH, is a valuable approach for routine clinical use in achieving a more complete genetic characterization of patients with PCN.

Patterns of expression of CD56 and CD117 on neoplastic plasma cells and association with genetically distinct subtypes of plasma cell myeloma

Plasma cell neoplasms are common hematopoietic malignancies that recently have been shown to be driven by specific genetic events. In the past decade, immunophenotyping by flow cytometry has become an important tool in the characterization of plasma cells. However, the clinical and prognostic significance of antigenic expression remains unclear. We analyzed 102 cases of plasma cell neoplasm by flow cytometric immunophenotyping for expression of CD56 and CD117 and correlated the results with immunohistochemical and cytogenetic findings. Expression of CD56 and CD117 was associated with hyperdiploidy and the absence of CD117 expression was associated with different immunoglobulin heavy chain gene (IGH) translocations. Assessment of CD117 expression on neoplastic plasma cells by flow cytometry is superior to immunohistochemistry. Simultaneous assessment of CD56 and CD117 expression by flow cytometry is a sensitive method for diagnostic evaluation of plasma cell neoplasms, and furthermore may function as a rapid adjunctive test providing independent prognostic information in the absence of cytogenetic data.

Detection of genomic abnormalities in multiple myeloma: the application of FISH analysis in combination with various plasma cell enrichment techniques

Multiple myeloma (MM) is a hematopoietic neoplasm characterized by malignant plasma cells (PCs) that accumulate in the bone marrow. A number of different genomic abnormalities are associated with MM; however, detection of these by fluorescence in situ hybridization (FISH) can be limited by the percentage of PCs in the specimen. In this study, we tested 20 bone marrow specimens with known MM and a low concentration of monoclonal PCs for the presence of genomic abnormalities using FISH in combination with various PC enrichment techniques: magnetic cell sorting, targeted manual scoring, and automated image analysis. In addition, flow cytometric cell sorting of PCs in combination with FISH analysis was also tested for minimal residual disease applications. Different parameters were evaluated when assessing the detection efficiency of each approach. FISH results are highly dependent on the chosen enrichment method. We describe the evaluation of different techniques applicable for various laboratory settings and specimen parameters.