Clonal origin of tumor cells in a plexiform neurofibroma with LOH in NF1 intron 38 and in dermal neurofibromas without LOH of the NF1 gene

Biochem Biophys Res Commun. 1997 May 19;234(2):346-50. doi: 10.1006/bbrc.1997.6645.


LOH at the NF1 locus was investigated in 38 neurofibromas of 26 NF1 patients. Only in one of these tumors LOH was observed. In this plexiform neurofibroma of a NF1 patient with a constitutional one base-pair insertion in NF1 exon 4b, a non-random X-inactivation pattern was found, strongly suggesting a clonal origin of the tumor cells. The analysis of X-inactivation patterns allowed the classification of some of the other neurofibromas with regard to the detectability of clonal LOH. In 3 of 6 neurofibromas without LOH amenable to this analysis, a comparable X-inactivation pattern was found in constitutional and neurofibroma derived DNA. A clonal LOH would not have been detected in these tumors. However, we observed a nonrandom pattern in 3 of the 6 neurofibromas, suggesting a clonal origin of the tumor cells. LOH was not detected in these tumors, but could, however, have occurred by mutational events below the level of large somatic deletions, loss of a whole chromosome 17 or somatic recombination.

Publication types

  • Case Reports
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Chromosomes, Human, Pair 17 / genetics
  • Dosage Compensation, Genetic
  • Female
  • Genes, Neurofibromatosis 1*
  • Genetic Markers
  • Heterozygote
  • Humans
  • Introns
  • Mutation
  • Neurofibroma / genetics*
  • Neurofibroma / pathology*
  • Neurofibroma, Plexiform / genetics*
  • Neurofibroma, Plexiform / pathology*
  • Neurofibromatosis 1 / genetics
  • Neurofibromatosis 1 / pathology
  • Polymorphism, Genetic
  • Receptors, Androgen / genetics
  • Recombination, Genetic
  • Skin Neoplasms / genetics*
  • Skin Neoplasms / pathology*


  • Genetic Markers
  • Receptors, Androgen