LILRB1: A Novel Diagnostic B-Cell Marker to Distinguish Neoplastic B Lymphoblasts From Hematogones.

OBJECTIVES: New B-cell markers are needed for monitoring B lymphoblastic leukemia (B-ALL) in the era of immunotherapies directed against CD19 and CD22. The expression of leukocyte immunoglobulin-like receptor subfamily B member 1 (LILRB1) on hematogones in bone marrow (BM) and neoplastic B lymphoblasts has not yet been systematically investigated. METHODS: We assessed LILRB1 expression pattern on B cells in 19 control BMs and 22 B-ALL cases by flow cytometry. RESULTS: In all cases, mature B cells and hematogones exhibited a consistent pattern of LILRB1 expression with variable intensity over different stages of maturation, including a characteristic V-shaped pattern on hematogones. While neoplastic B lymphoblasts in all cases expressed LILRB1, the pattern of expression was distinctly abnormal relative to hematogones (loss of the dynamic pattern in all cases and abnormal expression levels in 83% of cases). CONCLUSIONS: LILRB1 is a novel diagnostic B-cell marker to aid in distinguishing neoplastic B lymphoblasts from hematogones.

Bright CD38 Expression by Flow Cytometric Analysis Is a Biomarker for Double/Triple Hit Lymphomas with a Moderate Sensitivity and High Specificity.

BACKGROUND: High-grade B-cell lymphomas (HGBCL) with MYC and BCL2 or/and BCL6 rearrangements (R), so-called double/triple-hit lymphomas (DH/THL), are uncommon, clinically aggressive lymphomas that require a prompt diagnosis. We aim to identify flow cytometric immunophenotypic (IP) features of DH/THL that may aid in triaging these cases followed by a timely confirmatory cytogenetic study. METHODS: We compared the IP features of 43 cases of DH/THL to those of 55 cases of single-hit lymphoma (SHL) and 59 cases of diffuse large B-cell lymphoma (DLBCL) without MYC-R (MYCneg DLBCL). We analyzed the expression patterns of CD10, CD19, CD20, CD38, and surface immunoglobulin light chain in lymphoma cells. RESULTS: Bright CD38 expression (CD38bright ) analyzed either qualitatively or semi-quantitatively was more common in DH/THL (56%) than in MYCneg DLBCL (17%) but less common compared to SHL (82%), indicating that CD38bright can serve as a biomarker for DH/THL. Additionally, CD38bright may be a better indicator for predicting DH/THL-BCL2 than DHL-BCL6, and very bright CD38 expression was exclusive to MYC rearranged lymphomas. The expression patterns of other markers were similar among these lymphoma groups. CONCLUSIONS: CD38bright is a biomarker associated with DH/THL with a moderate sensitivity (~50%) and high specificity (~90%). While this marker cannot be used as a screening tool, awareness of this correlation may aid in expediting the diagnosis and prioritizing FISH testing in resource limited settings or situations when samples are limited. Future studies to combine immunohistochemical markers are needed to further enhance the predictive power of CD38bright in diagnosing DH/THL. © 2019 International Clinical Cytometry Society.