Loss of heterozygosity in tumor cells of a recurrent mandibular giant cell granuloma in neurofibromatosis type 1.

Neurofibromatosis type 1 (NF1) is an autosomal dominant inherited disease affecting about 1:3000 humans. Neurofibromas are benign soft tissue tumors. Giant cell granuloma (GCG) is a benign tumor-like lesion that is preferentially located in the jaws. GCG can develop in NF1 patients. A 7-year-old female NF1 patient was successfully treated for a recurrent GCG of the right mandibular premolar region. The serum levels of calcium and phosphate, alkaline phosphatase and parathormone were within the normal range. Genetic analysis of the tumor sample (GCG) and blood using 7 microsatellite markers revealed LOH of the NF1 gene in both sources. Inactivation of the NF1 gene may thus contribute to the development of GCG.