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Atoll sign or reversed halo sign? Which term should be used?
  1. Edson Marchiori1,
  2. Klaus L Irion2,
  3. Gláucia Zanetti1,
  4. Bruno Hochhegger1
  1. 1Rio de Janeiro Federal University, Rio de Janeiro, Brazil
  2. 2Liverpool Heart and Chest Hospital, NHS Trust, Liverpool, UK
  1. Correspondence to Edson Marchiori, Rio de Janeiro Federal University, Rio de Janeiro, Brazil, Rua Thomaz Cameron, 438. Valparaiso, Petrópolis 25.685.120, Brazil; edmarchiori{at}

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We read with great interest the article by Walsh and Robertson1 reporting a case of cryptogenic organising pneumonia. The authors included wonderful images of a CT pattern they called the ‘atoll sign’, which has been described by other authors as the ‘reversed halo sign’.

Zompatori et al2 first used the term ‘atoll sign’ in 1999 to describe the imaging finding of a focal rounded area of ground-glass opacity surrounded by a more or less complete ring of consolidation.3 Although the abnormality frequently resembles an atoll, the Fleischner Society4 prefers the term ‘reversed halo sign’, as initially proposed by Kim et al.3 Although both terms adequately describe the imaging characteristics of the lesion, the term ‘reversed halo sign’ should be used to avoid confusion and to standardise the keywords used in literature searches. A review of the US National Institutes of Health digital archive of biomedical and life sciences journal literature (PubMed) found only three occurrences of the term ‘atoll sign’, whereas the term ‘reversed halo sign’ was found in 22 articles. The uniform use of descriptors is critical when reporting on lesions, to avoid the overlooking of otherwise important articles, such as the one presented by Walsh and Robertson, in literature reviews.



  • Competing interests None.

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

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