September 2021 – Hematopathology

A 14-year-old girl with recurrent tonsillar infections had tonsillectomy. Bilateral palatine tonsils and right lingual tonsil were excised and submitted for histologic examination. Hematoxylin and eosin and immunohistochemical stains are shown (Fig.1 and 2). 

Figure 1: IRF4
Figure 2: IRF4

If you can perform only one additional ancillary test to confirm the diagnosis, which one would you choose?

  • FISH for IRF4 rearrangement
  • In situ hybridization for EBV
  • FISH for MYC rearrangement
  • Molecular study for MYD88 mutation

The correct answer is ...

The correct answer is: FISH for IRF4 rearrangement.

The clinical scenario, neoplastic cells morphology and immunohistochemical stains (neoplastic cells express CD20, CD10, BCL6 and MUM1), suggest that the patient has large B-cell lymphoma with IRF4 rearrangement. This diagnosis needs to be distinguished from other large B-cell neoplasms because the patients have a favorable outcome after treatment. 

Incorrect answer: Molecular studies for MYD88 mutation is important when lymphoplasmacytic lymphoma is in the differential. Cells morphology and immunohistochemical profile in this cases make lymphoplasmacytic lymphoma an unlikely diagnosis.

Incorrect answer: FISH for IRF4 rearrangement should be performed first, and if the result is negative, FISH for MYC, BCL2, and BCL6 rearrangement should be considered for differential diagnosis of diffuse large B-cell lymphoma and high-grade B-cell lymphoma with MYC/BCL and/or BCL6 rearrangement.

Incorrect answer: Epstein-Barr virus has not been linked to pathogenesis of large B-cell lymphoma with IRF4 rearrangement.


  1. Swerdlow S, Campo E, Harris NL, Jaffe E, Pileri S, Stein H, Thiele J, Arber D, Hasserjian R, Le Beau M. WHO classification of tumours of haematopoietic and lymphoid tissues (Revised 4th edition). IARC: Lyon 2017.
  2. Woessmann W, Quintanilla-Martinez L. Rare mature B-cell lymphomas in children and adolescents. Hematol Oncol. 2019 Jun;37 Suppl 1:53-61. doi: 10.1002/hon.2585. PMID: 31187530.Granai M, Lazzi S. Early pattern of large B-cell lymphoma with IRF4 rearrangement. Blood. 2020 Aug 6;136(6):769. doi: 10.1182/blood.2020006406. PMID: 32761226

Krasimira Rozenova, M.D., Ph.D.

Resident, Anatomic and Clinical Pathology
Mayo Clinic

Rebecca King, M.D.

Consultant, Hematopathology
Mayo Clinic
Associate Professor of Laboratory Medicine and Pathology
Mayo Clinic College of Medicine and Science

MCL Education

This post was developed by our Education and Technical Publications Team.