Role of Flow Cytometric Immunophenotyping for Classic Hodgkin Lymphoma in Small Biopsy and Cytology Specimens

Flow Cytometry for B-Cell Non-Hodgkin and Hodgkin Lymphomas

Multi-parametric flow cytometry is a powerful diagnostic tool that permits rapid assessment of cellular antigen expression to quickly provide immunophenotypic information suitable for disease classification. This chapter describes the classification of B-cell non-Hodgkin lymphoma (B-NHL) by flow cytometry suitable for the clinical and research environment. In addition to describing the immunophenotypic patterns of the most common B-NHL (including examples of common B-NHL), the effect of anti-CD19, -CD20, and -CD38 therapies on the evaluation of flow cytometric data is also discussed. Over the last 15 years, our laboratory has developed flow cytometry combinations that can immunophenotype classic Hodgkin lymphoma (CHL), nodular lymphocyte predominant Hodgkin lymphoma (NLPHL), and T-cell/histocyte-rich large B-cell lymphoma (THRLBCL) and the use of these assays will be presented. The CHL assay combination is also particularly well suited to immunophenotype primary mediastinal large B-cell lymphoma (PMLBCL) and our experience immunophenotyping PMLBCL by flow cytometry will be discussed. Finally, an approach to the evaluation of the reactive infiltrate of CHL, NLPHL, and THRLBCL that can provide diagnostic information will also be provided.

Utility of CCR7 to differentiate classic Hodgkin lymphoma and other B-cell lymphomas by flow cytometry and immunohistochemistry

OBJECTIVES

Classic Hodgkin lymphoma (CHL) is characterized by infrequent neoplastic Hodgkin and Reed-Sternberg (HRS) cells in an inflammatory background. The diagnostic utility of CC-chemokine receptor 7 (CCR7) in CHL was explored using flow cytometry and immunohistochemistry (IHC).

METHODS

Neoplastic specimens and non-neoplastic lymph nodes were immunophenotyped and CCR7 expression was measured semiquantitatively by flow cytometry (clone 3D12) and IHC (clone 150503).

RESULTS

Our results showed that CCR7 was expressed on HRS cells in the vast majority of CHL cases (45/48 by flow cytometry, 57/59 by IHC) but rarely expressed in neoplastic cells in diffuse large B-cell lymphoma, not otherwise specified (1/25 by flow cytometry, 2/40 by IHC) and nodular lymphocyte predominant Hodgkin lymphoma (0/4 by flow cytometry, 1/13 by IHC). Primary mediastinal large B-cell lymphoma (PMLBCL) revealed weak CCR7 expression by flow cytometry in most cases (8/10) but only occasionally by IHC (2/12). Both cases (2/2) of T-cell/histiocyte-rich large B-cell lymphoma (THRLBCL) also showed CCR7 expression detected by flow cytometry compared with IHC (0/7). The HRS cells demonstrated a greater percentage of positive cells and greater antigen intensity than the other B-cell lymphomas by IHC. The expression identified by flow cytometry in PMLBCL and THRLBCL but not by IHC suggests that there may be differences in the detection capabilities of the 2 techniques or the 2 CCR7 clones used.

CONCLUSIONS

The expression of CCR7 in HRS cells suggests its potential utility in differentiating CHL from other B-cell lymphomas. Incorporating CCR7 into flow cytometry and IHC panels may further enhance the diagnostic sensitivity of CHL.

Flow Cytometry for Non-Hodgkin and Hodgkin Lymphomas

Multiparametric flow cytometry is a powerful diagnostic tool that permits rapid assessment of cellular antigen expression to quickly provide immunophenotypic information suitable for disease classification. This chapter describes a general approach for the identification of abnormal lymphoid populations by flow cytometry, including B, T, NK, and Hodgkin lymphoma cells suitable for the clinical and research environment. Knowledge of the common patterns of antigen expression of normal lymphoid cells is critical to permit identification of abnormal populations at disease presentation and for minimal residual disease assessment. We highlight an overview of procedures for processing and immunophenotyping non-Hodgkin B- and T-cell lymphomas and also describe our strategy for the sensitive and specific diagnosis of classic Hodgkin lymphoma, nodular lymphocyte predominant Hodgkin lymphoma, and T-cell/histiocyte-rich large B-cell lymphoma.

Utility of fine-needle aspiration cytology combined with flow cytometry in extramedullary hematolymphoid lesions - A cross-sectional study

Objective

Flow cytometry (FC) can be an adjunct to fine-needle aspiration cytology (FNAC) in the diagnosis and subclassification of hematolymphoid lesions. This study evaluates the utility of FC in diagnosing extramedullary hematolymphoid lesions in fine-needle aspirate samples.

Material and Methods

This cross-sectional study enrolled patients who presented to the FNAC clinic and suspected to have hematolymphoid lesions (nodal and extra nodal lesions) from August 2020 to June 2022. Sixty-seven cases of hematolymphoid malignancies and 67 cases without hematolymphoid malignancies were included. The combined FNAC/FC diagnosis was compared with the gold standard: Biopsy, cell block, or peripheral blood/bone marrow aspirate FC.

Results

Of 67 lymphoma cases, 63 were of the primary type and 4 were diagnosed with suspected recurrence/residual disease. Moreover, 57 cases were nodal, and 10 were extranodal. Four of the patients had discordant findings between FNAC and FC. The gold standard was available only in 56 cases, of which 5 had discordant findings between combined FNAC/FC and the gold standard. We subclassified 34 cases based on combined FNAC/FC. The five cases included anaplastic large cell lymphoma (1/5), classic Hodgkin lymphoma (3/5), and one case of atypical lymphoid hyperplasia. Non-contributory FC was attributed to the presence of large cells/necrosis/nodular lymphocyte predominant Hodgkin lymphoma/metastasis/Castleman disease/technical problem.

Conclusion

Combining FC with FNAC enhances diagnostic accuracy and helps subclassify lymphoma. Future works should explore whether it can replace excision biopsy, especially in recurrent cases.

Implicit Flow Cytometric Diagnosis of Classic Hodgkin Lymphoma Using CD3+CD4+CD26- T-Cells

BACKGROUND

Flow cytometry is not routinely performed in clinical laboratories for the diagnosis of classic Hodgkin lymphoma (CHL).

METHODS

Fourteen cases of CHL and 132 cases of the control group were studied by 10-color flow cytometry, with markers including CD3, CD4, CD7, CD8, and CD26, as well as calculated parameters such as the CD4:CD8 ratio, percent CD3+CD4+CD26- T-cells of CD3+CD4+ T-cells, percent CD3+CD4+CD26- T-cells of total events, CD7 coefficient of variation among CD3+CD4+CD26- T-cells, and CD7 median fluorescence intensity of CD3+CD4+CD26- T-cells relative to CD3+CD8+ T-cells.

RESULTS

CHL cases showed a median percent CD3+CD4+CD26- of CD3+CD4+ T-cells of 72.3% with range from 41.1% to 94.4%, median percent CD3+CD4+CD26- T-cells of total events of 17.4% with range from 4.6% to 52.5%, CD7 coefficient of variation among CD3+CD4+CD26- T-cells less than 100%, and CD7 median fluorescence intensity of CD3+CD4+CD26- T-cells relative to CD3+CD8+ T-cells of 1.7 with range from 0.4 to 3.5. In the control group, every entity showed some degree of overlap with CHL in terms of these parameters. A "Hodgkin score" was thus constructed to enhance separation of CHL from other entities. A threshold Hodgkin score of 15.35 achieved a sensitivity of 78.6% and specificity of 96.2% in the diagnosis of CHL. Incorporating the Hodgkin score into a simple algorithm raises the specificity to 100%.

CONCLUSION

In this study, we used flow cytometry to demonstrate increased CD3+CD4+CD26- T-cells in CHL, and derived a Hodgkin score for the diagnosis of CHL.

The biology of classical Hodgkin lymphoma

Classical Hodgkin lymphoma (cHL) is distinguished by several important biological characteristics. The presence of Hodgkin Reed Sternberg (HRS) cells is a defining feature of this disease. The tumor microenvironment with relatively few HRS cells in an expansive infiltrate of immune cells is another key feature. Numerous cell-cell mediated interactions and a plethora of cytokines in the tumor microenvironment collectively work to promote HRS cell growth and survival. Aberrancy and constitutive activation of core signal transduction pathways are a hallmark trait of cHL. Genetic lesions contribute to these dysregulated pathways and evasion of the immune system through a variety of mechanisms is another notable feature of cHL. While substantial elucidation of the biology of cHL has enabled advancements in therapy, increased understanding in the future of additional mechanisms driving cHL may lead to new treatment opportunities.

Role of flow cytometric immunophenotyping in the diagnosis of breast implant-associated anaplastic large cell lymphoma: A 6-year, single-institution experience

Breast implant-associated anaplastic large cell lymphoma (BIA-ALCL) is an uncommon mature T-cell neoplasm occurring in patients with textured breast implants, typically after 7-10 years of exposure. Although cytopathologic or histopathologic assessment is considered the gold standard diagnostic method for BIA-ALCL, flow cytometry (FC)-based immunophenotyping is recommended as an adjunct test. However, the diagnostic efficacy of FC is not well reported. We reviewed 290 FC tests from breast implant pericapsular fluid and capsule tissue from 182 patients, including 16 patients with BIA-ALCL over a 6-year period, calculating diagnostic rates and test efficacy. FC showed an overall sensitivity of 75.9%, specificity of 100%, and negative and positive predictive values of 95.4% and 100%, respectively. Blinded expert review of false-negative cases identified diagnostic pitfalls, improving sensitivity to 96.6%. Fluid samples had better rates of adequate samples for FC testing compared with tissue samples. Paired with FC testing of operating room (OR)-acquired fluid samples, capsulectomy FC specimens added no diagnostic value in patients with concurrent fluid samples; no cases had positive capsule FC with negative fluid FC. Fluid samples are adequate for FC testing more often than tissue. Capsule tissue FC specimens do not improve FC efficacy when paired with OR-acquired fluid FC samples and are often inadequate samples. FC is 100% specific for BIA-ALCL and can serve as a confirmatory test but should not be the sole diagnostic method. Awareness of sample-specific diagnostic pitfalls greatly improves the sensitivity of BIA-ALCL testing by FC.

Pitfalls in Lymph Node Fine Needle Aspiration Cytology

BACKGROUND

Fine needle aspiration cytology (FNAC) is an accurate, minimally invasive, and cost-effective biopsy method for enlarged lymph nodes. While the role of lymph node FNAC in the diagnosis of infectious or reactive conditions and metastatic malignancy is unquestioned, differing views still exist on its role in the diagnosis of lymphoma. Nevertheless, regardless of the practice setting, pitfalls and potential for error exist, and it is incumbent upon the pathologist to be aware of these pitfalls, as this is the first line of defence against errors.

SUMMARY

This discussion will focus on potential interpretational errors, specifically highlighting scenarios leading to false-negative and false-positive diagnosis and errors in tumour classification, with an emphasis on cytomorphology. Potential entities that may fly below the radar of the pathologist - so-called off-radar entities - are also discussed, as a reminder to consider broad differentials in cases with unusual morphologic features. Some reasons for false-negative diagnoses include low-grade lymphomas that mimic a mixed, polymorphous reactive lymphoid population or aspirates with a paucity of lesional cells, through either sampling error or the intrinsic nature of the entity, e.g., nodular lymphocyte predominant Hodgkin lymphoma. Some of the potential causes of false-positive diagnoses that are discussed include viral-associated lymphadenopathy, Kikuchi-Fujimoto lymphadenitis, or benign adnexal lesions mimicking metastatic malignancy. Errors in tumour classification covered include metastatic carcinoma, sarcoma, melanoma, and lymphoma mimicking each other, and Hodgkin lymphoma and its mimics. Finally, less common entities such as follicular dendritic cell sarcoma and others are briefly mentioned, to remind us of conditions that may slip under our diagnostic radar.

KEY MESSAGES

A systematic review of diagnostic pitfalls and traps is elucidated here, with some tips to avoid these traps. The triple approach to the diagnostic workup is emphasised, which includes rigorous clinicopathologic correlation, attention to cytomorphology, and judicious application of ancillary tests.

Endoscopic Ultrasound-Guided Fine Needle Biopsy in the Diagnostic Work-Up of Deep-Seated Lymphadenopathies and Spleen Lesions: A Monocentric Experience

EUS-FNB has been introduced in clinical practice as a less invasive diagnostic approach with respect to surgery. We performed a single-center retrospective study on the diagnostic efficacy of EUS-guided FNB, including 171 patients with lymph nodes, splenic, and extranodal lesions that underwent EUS for FNB at our institution. Excluding 12 patients who did not undergo FNB and 25 patients with a previous diagnosis of a solid tumor, we included 134 patients with clinical/radiological suspect of a lymphoproliferative disease, including 20 patients with a previous history of lymphoma. Out of the 134 biopsies, material of diagnostic quality was obtained in 111 procedures (84.3%). Histological examination of the EUS-FNB samples produced an actionable diagnosis in 100 cases (74.6%). Among the patients without an actionable diagnosis, a second, different diagnostic procedure produced a further eight diagnoses of lymphoma. Therefore, the sensitivity of EUS-FNB for diagnosing lymphomas was calculated to be 86.4% (51/59). Assignment of lymphomas to WHO classification subtypes was possible in 47/51 (92%) of the cases. In conclusion, EUS-FNB is an effective procedure for the histological characterization of lesions that are suspected to be lymphoproliferative disease, allowing for an actionable diagnosis in 75% of cases.

A Review of the Flow Cytometric Findings in Classic Hodgkin Lymphoma, Nodular Lymphocyte Predominant Hodgkin Lymphoma and T Cell/Histiocyte-Rich Large B Cell Lymphoma

Classic Hodgkin lymphoma, nodular lymphocyte predominant Hodgkin lymphoma, and T cell/histiocyte-rich large B cell lymphoma form a unique set of lymphomas with similar morphologic growth patterns (occasional neoplastic cells within a prominent cellular cell background) that are pathobiologically related. Distinguishing these entities has been historically difficult by flow cytometry; however, our laboratory has developed antibody-fluorochrome combinations capable of immunophenotyping these lymphomas. Additionally, characterization of the background reactive lymphocytes can aid in narrowing the differential diagnosis. This review summarizes the immunophenotypic features and insights of the neoplastic and reactive populations found in this unique group of lymphomas.

Flow cytometry assessment of reactive T-cells distinguishes classic Hodgkin lymphoma from benign lymphadenopathy in children

Background

Detection of classic Hodgkin lymphoma (cHL) neoplastic cells using flow cytometric immunophenotyping (FCI) remains limited. We hypothesized that characterization of the reactive infiltrates could assist in diagnosing cHL in children.

Methods

FCI using four‐color staining approaches was performed on 156 lymph node specimens with the following histopathologic diagnoses: cHL (25 cases), reactive lymphoid hyperplasia (RLH, 44 cases), and non‐Hodgkin lymphoma (87 cases).

Results

The overall concordance of FCI data with the histopathologic results of these cases was 81.4%. A reactive expansion of T‐cells with increased expression of CD45RO was present in the reactive infiltrate of cHL (CD45RO/CD3, 67.5%) and Epstein–Barr virus (EBV) infected RLH (62.7%) but not in EBV‐negative RLH (28.0%). The mean fluorescence intensity (MFI) of CD7 was higher for cHL and differed significantly from EBV‐positive RLH (138.5 vs. 63.8). A proposed diagnostic algorithm markedly elevated the overall concordance rate from 81.4% to 97.4%.

Conclusions

Immunophenotyping the reactive infiltrate of lymphoid tissue using flow cytometry is a reliable supplement to histopathology for the rapid diagnosis of pediatric cHL.