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Letter to the editor
Nuclear smears observed in H&E-stained thrombus sections are neutrophil extracellular traps
  1. Onno J de Boer1,
  2. Xiaofei Li1,
  3. Heike Goebel2,
  4. Allard C van der Wal1
  1. 1Department of Pathology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
  2. 2Department of Pathology, University of Koln, Köln, Germany
  1. Correspondence to Dr Onno J de Boer, Department of Pathology, Academic Medical Center, Meibergdreef 9, Amsterdam 1105 AZ, The Netherlands; o.j.deboer{at}

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Chromatin-rich smears are well-recognised artefacts in H&E sections, which may result from nuclear fragility and tissue crushing. Less well known among surgical pathologists is a novel, recently discovered form of cell death called ‘NETosis’, which at the light microscopical level closely resembles such crush artefacts.

Figure 1A shows an H&E stain of thrombus obtained from human aorta. Besides platelets, fibrin and red blood cells, this type of specimens often contain large numbers of neutrophils.1 In this image, deep purple stained treads of variable length and often clustered can be noticed, which will easily be interpreted as a crush artefact. However, these structures are, in fact, neutrophil extracellular traps (NETs).

Figure 1

Sequential (immune)staining on human aortic thrombus: H&E (A), citrullinated histone-3 (B) and MPO (C). In (D), a false-colour composite image generated from (B) and (C) is illustrated, showing citrullinated histone 3 in red, MPO in green and double staining in yellow. Note that citrullinated histone 3+MPO+ areas correspond with the ‘haematoxylin smears’. In addition, it can be appreciated that only a subpopulation of the neutrophils undergo NETosis. (E) shows the negative control after one elution round. Bar=50 micron. NETosis, cell death with the release of neutrophil extracellular traps.

In 2004, Brinkmann showed that …

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  • Contributors This letter was conceived by all authors. The first version of the letter was prepared by OJdB and ACvdW, and XL and HG contributed to the final version.

  • Competing interests None declared.

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