Flow Cytometry Immunophenotyping for Diagnostic Orientation and Classification of Pediatric Cancer Based on the EuroFlow Solid Tumor Orientation Tube (STOT)

Implementation of flow cytometry testing on rare matrix samples: Special considerations and best practices when the sample is unique or difficult to obtain

The publication of Clinical and Laboratory Standards Institute's guideline H62 has provided the flow cytometry community with much-needed guidance on development and validation of flow cytometric assays (CLSI, 2021). It has also paved the way for additional exploration of certain topics requiring additional guidance. Flow cytometric analysis of rare matrices, or unique and/or less frequently encountered specimen types, is one such topic and is the focus of this manuscript. This document is the result of a collaboration subject matter experts from a diverse range of backgrounds and seeks to provide best practice consensus guidance regarding these types of specimens. Herein, we define rare matrix samples in the setting of flow cytometric analysis, address validation implications and challenges with these samples, and describe important considerations of using these samples in both clinical and research settings.

Detection of Nonhematologic Neoplasms in Bone Marrow by Flow Cytometry: A Report of Two Cases

Multiparameter flow cytometry (MFC) is a well-established method for the diagnosis, prognosis, and follow-up of a vast majority of hematological malignancies; however, it can have a major impact on the rapid diagnosis of nonhematopoietic tumor micrometastases in minimally invasive samples such as bone marrow aspirates (BMAs), body fluids, and tissue samples (lymph nodes, fine needle aspirates). Here, we present two cases of bone marrow micrometastases of neuroendocrine origin (one small cell lung carcinoma [SCLC] and one large cell neuroendocrine carcinoma [LCNEC] of the lungs) readily recognized by routine MFC investigation of BMA and review the existing literature on the role of MFC in the diagnosis of solid tumors of neuroendocrine origin. The clinical application of flow cytometry for the diagnosis of solid tumors is limited despite the accumulating evidence of the value of the method. It can be of great value in situations where the patient's clinical status forbids invasive procedures, and a rapid diagnosis is desirable. Flow cytometry is a valuable tool for the detection of both hematological and nonhematologic neoplasms. Future large-scale patient series will probably confirm its role in the screening, diagnosis, and classification of more tumor types.

High sensitivity flow cytometry immunophenotyping increases the diagnostic yield of malignant pleural effusions

Diagnosing malignant pleural effusions (MPE) is challenging when patients lack a history of cancer and cytopathology does not detect malignant cells in pleural effusions (PE). We investigated whether a systematic analysis of PE by flow cytometry immunophenotyping (FCI) had any impact on the diagnostic yield of MPE. Over 7 years, 570 samples from patients with clinical suspicion of MPE were submitted for the FCI study. To screen for epithelial malignancies, a 3-color FCI high sensitivity assay was used. The FCI results, qualified as "malignant" (FCI+) or "non-malignant" (FCI-), were compared to integrated definitive diagnosis established by clinicians based on all available information. MPE was finally diagnosed in 182 samples and FCI detected 141/182 (77.5%). Morphology further confirmed FCI findings by cytopathology detection of malignant cells in PE (n = 91) or histopathology (n = 29). Imaging tests and clinical history supported the diagnosis in the remaining samples. The median percentage of malignant cells was 6.5% for lymphoma and 0.23% for MPE secondary to epithelial cell malignancies. FCI identified a significantly lower percentage of EpCAM+ cells in cytopathology-negative MPE than in cytopathology-positive cases (0.02% vs. 1%; p < 0.0001). Interestingly, 29/52 MPE (55.8%) where FCI alerted of the presence of malignant cells were new diagnosis of cancer. Overall, FCI correctly diagnosed 456/522 samples (87.4%) suitable for comparison with cytopathology. These findings show that high sensitivity FCI significantly increases the diagnostic yield of MPE. Early detection of FCI + cases accelerates the diagnostic pathway of unsuspected MPE, thus supporting its implementation in clinical diagnostic work-up as a diagnostic tool.

Utility of Flow Cytometry Analysis in the Detection of Nonhematologic Neoplasms: An Overview

Flow cytometry analysis has stood the test of time as a powerful tool in the assessment of hematologic neoplasms. The role of flow cytometry has expanded to evaluate various nonhematologic neoplasms encountered in body cavity malignant effusions, lymph nodes, and other body sites. This review explores the use of routine antibody panels as well as specially designed multicolor antibody panels that have been investigated by different groups and reported in the literature for evaluating nonhematologic neoplasms. In this context, the limitations, pitfalls, future directions, and promising applications of flow cytometry analysis are also discussed.

Routine flow cytometry approach for the evaluation of solid tumor neoplasms and immune cells in minimally invasive samples

BACKGROUND

Multidimensional flow cytometry (MFC) is routinely used for the diagnosis and follow-up of hematolymphoid neoplasms but its contribution to the identification of non-hematolymphoid malignant tumors is limited.

METHODS

The presence of non-hematolymphoid cells in clinical samples obtained via minimally invasive methods was ascertained by using a panel of monoclonal antibodies previously developed in our laboratory comprising a mixture of antibodies: CD9-PacB/CD45-OC515/CD57-FITC/CD56-PE/CD3-PerCP-Cy5.5/CD117-PE-Cy7/CD326-APC/CD81-APC-C750. Histopathological studies were performed using standard techniques.

RESULTS

164 specimens of different origins were included. Malignancy was finally confirmed in 142 (86.5%), while 22 non neoplastic samples were identified. The most frequent diagnosis was small cell lung carcinoma (SCLC) (50%). High sensitivity (S = 98.6%) was reached combining MFC and conventional pathology. Individual markers differed according to the cellular origin of the neoplasm, with neuroendocrine tumors showing a unique immunophenotypic profile (CD56+ CD326+ CD117-/+ and variable tetraspanins expression). Principal component analysis efficiently distinguished SCLC from other tumor samples. In immune cell populations, differences between reactive and malignant biopsies were found in different cell compartments, especially in B cells and Plasma cells. Differences also emerged in the percentage of CD4+ CD8- T cells, CD4-CD8+ T cells and NK cells and these were dependent on the origin of the tumor cells.

CONCLUSIONS

These results support the use of MFC as a rapid and valuable technique to detect non-hematolymphoid tumoral cells in clinical specimens, providing an initial orientation to complement hystopathological studies and allow a more precise diagnosis, especially in neuroendocrine neoplasms. The impact of different immune cell patterns warrants further research.