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Contributors JC wrote the manuscript. JC, AP and ER reviewed the literature and collected the images. All authors edited the manuscript. JC is the article guarantor.
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.
Patient consent for publication Obtained.
Provenance and peer review Not commissioned; externally peer reviewed.
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