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Mosaicism for oncogenic G12D KRAS mutation associated with epidermal nevus, polycystic kidneys and rhabdomyosarcoma
  1. Franck Bourdeaut1,2,3,
  2. Aurélie Hérault3,4,
  3. David Gentien5,
  4. Gaëlle Pierron6,
  5. Stelly Ballet6,
  6. Stéphanie Reynaud6,
  7. Régine Paris7,
  8. Gudrun Schleiermacher2,3,8,
  9. Clarisse Baumann9,
  10. Pascale Philippe-Chomette10,
  11. Marion Gauthier-Villars11,
  12. Michel Peuchmaur7,12,
  13. François Radvanyi3,4,
  14. Olivier Delattre2,3,6
  1. 1CHU Nantes, Service d'oncologie pédiatrique, Nantes, France
  2. 2INSERMU830, Laboratoire de biologie et génétique des cancers, Paris, France
  3. 3Institut Curie, Centre de recherche, Paris, France
  4. 4CNRS, U144, 2 rue Lhomond, Institut Curie, Paris, France
  5. 5Institut Curie, Département de transfert, 1 avenue Claude Vellefaux, Paris, France
  6. 6Institut Curie, Unité de génétique somatique, Paris, France
  7. 7Hôpital Robert Debré, Service d'anatomie pathologique, Paris, France
  8. 8Institut Curie, Département de pédiatrie, Paris, France
  9. 9Hôpital Robert Debré, Service de génétique, Paris, France
  10. 10Hôpital Robert Debré, Service de chirurgie infantile, 49 boulevard Serrurier, Paris, France
  11. 11Institut Curie, Département d'oncologie génétique, Paris, France
  12. 12Université Paris XI, Paris, France
  1. Correspondence to Dr Olivier Delattre, INSERM U830, Institut Curie, 26 rue d'Ulm 75248 Paris Cedex 05, France; Olivier.delattre{at}


Background Epidermal nevus (EN) is a congenital disorder characterised by hyperpigmented epidermal thickening following a Blaschko's line. It is due to somatic mutations in either FGFR3 or PIK3CA in half of the cases, and remains of unknown genetic origin in the other half. EN is also seen as part of complex developmental disorders or in association with bladder carcinomas, also related to FGFR3 and PIK3CA mutations. Mosaic mutations of these genes have been occasionally found in syndromic EN.

Case report The co-occurrence of EN, rhabdomyosarcoma, polycystic kidneys and growth retardation in an infant is described.

Results An oncogenic G12D KRAS mutation was detected in both the epidermal component of the EN and in the rhabodmyosarcoma but not in the dermal component of the EN lesion or in unaffected tissues, including normal skin or blood.

Conclusion This report shows for the first time that a KRAS mutation in epiderma causes EN. Observation of the same G12D KRAS mutation in two distinct regions of the body strongly suggests a somatic mosaicism. Finally, this report highlights the potentially underestimated importance of mosaic oncogene mutations in childhood cancers.

  • Mosaicism
  • KRAS
  • rhabdomyosarcoma
  • epidermal nevus
  • dermatology
  • genetics
  • paediatric oncology

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  • Funding This work was supported by grants from the INCa (plateforme de génétique moléculaire des cancers) and the Ligue Nationale Contre le Cancer (Equipes labellisées: FB, OD and AH, FR).

  • Competing interests None declared.

  • Patient consent Obtained.

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