Neurofibromatosis 1 phenotype associated to malignant peripheral nerve sheath tumours: a case-control study.

Background: Malignant peripheral nerve sheath tumours (MPNSTs) are the main cause of death in neurofibromatosis 1 adult patients.

Objective: To determine the clinical type of neurofibromas associated to MPNSTs.

Methods: Case-control study. Cases were neurofibromatosis 1 adults with MPNSTs and controls were patients without MPNSTs individually matched by age and sex (1 : 3). Both were recruited from our database. The following variables were studied: clinical presence of cutaneous, subcutaneous or plexiform neurofibromas and of internal neurofibromas. Internal neurofibromas were confirmed by clinical imaging. Multivariate odds ratios (aORs) were estimated with their 95% confidence interval (CI).

Results: From January 1995 to December 2007, 52 patients (cases) were identified with a MPNSTs, 155 controls could be recruited. In the multivariate analysis, MPNSTs were significantly associated with the presence of internal NFs (aOR: 7.5; 95% CI: 3.2-17.4), a trend for an association was observed for the presence of subcutaneous neurofibromas (aOR: 2.11; 95% CI: 0.89-5).

Conclusions: This study confirms the association between the MPNSTs and the internal neurofibromas. The later are indeed associated with a high risk of malignant transformation.