Association of myelodysplastic syndrome with CD5+, CD23+ monoclonal B-cell lymphocytosis

Lymphoid aggregates in bone marrow: a diagnostic pitfall

Lymphoid aggregates in bone marrow specimens are a relatively frequent finding that may pose a diagnostic challenge for a pathologist. The distinction between reactive and neoplastic aggregates has significant clinical relevance. Although many testing modalities such as immunohistochemistry, flow cytometry and molecular studies are currently available in clinical laboratories, the appropriate utilisation of these modalities and the awareness of their potential pitfalls are important. When a neoplastic process is ruled out, the significance of benign lymphoid aggregates in bone marrow is often unclear, as they may be associated with a broad spectrum of conditions including infections, autoimmune disorders, medications, or may even be idiopathic.This review focuses on evidence-based criteria that can aid in making the distinction between benign and malignant lymphoid aggregates and discusses the advantages, disadvantages and limits of ancillary tests used for this purpose. Finally, the most common aetiologies of benign lymphoid aggregates and their associations with specific diseases are discussed.

Subjects with chronic lymphocytic leukaemia-like B-cell clones with stereotyped B-cell receptors frequently show MDS-associated phenotypes on myeloid cells

An increasing body of evidence suggests the potential occurrence of antigen encounter by the cell of origin in chronic lymphocytic leukaemia (CLL) and CLL-like monoclonal B-cell lymphocytosis (MBL). However, the scenario in which this event might occur remains unknown. In order to gain insight into this scenario we investigated the molecular, cytogenetic and haematological features of 223 CLL-like (n = 84) and CLL (n = 139) clones with stereotyped (n = 32) versus non-stereotyped (n = 191) immunoglobulin heavy chain variable region (IGHV) amino acid sequences. Overall, stereotyped CLL-like MBL and CLL clones showed a unique IGHV profile, associated with higher IGHV1 and lower IGHV3 gene family usage (P = 0·03), longer IGHV complementary determining region 3 (HCDR3) sequences (P = 0·007) and unmutated IGHV (P < 0·001) versus non-stereotyped clones. Whilst the overall size of the stereotyped B-cell clones in peripheral blood did not appear to be associated with the CLL-related cytogenetic profile of B-cells (P > 0·05), it did show a significant association with the presence of myelodysplastic syndrome (MDS)-associated immunophenotypes on peripheral blood neutrophils and/or monocytes (P = 0·01). Altogether our results point to the potential involvement of different selection forces in the expansion of stereotyped vs. non-stereotyped CLL and CLL-like MBL clones, the former being potentially favoured by an underlying altered haematopoiesis.