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Lymphoid aggregates in bone marrow: a diagnostic pitfall
  1. Umberto Maccio1,
  2. Anton V Rets2,3
  1. 1 Pathology, University Hospital Zurich, Zürich, Switzerland
  2. 2 Hematopathology, ARUP Laboratories, Salt Lake City, Utah, USA
  3. 3 Pathology, University of Utah School of Medicine, Salt Lake City, Utah, USA
  1. Correspondence to Professor Anton V Rets, ARUP Laboratories, Salt Lake City, Utah, USA; Anton.Rets{at}


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.

  • bone marrow
  • lymphoma
  • lymphocytes
  • bone marrow diseases

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  • Handling editor Tahir S Pillay.

  • Contributors UM: ideated and designed the review, searched through the literature, interpreted clinical and research data, drafted the paper. AVR: designed the review, searched through the literature, interpreted clinical and research data, provided photos and drafted the paper.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; externally peer reviewed.