The neurofibromatosis type I gene encodes a protein, neurofibromin, which may 
function as a tumor suppressor gene product. Recent studies have demonstrated 
loss of neurofibromin in tumors from NF1 and non-NF1 patients, including 
neurofibrosarcomas, neuroblastomas and malignant melanomas. Since neurofibromin 
is expressed in the adrenal gland, six pheochromocytomas and one adrenal 
cortical tumor were examined for neurofibromin expression. In all seven tumors, 
no neurofibromin could be detected. Furthermore, loss of heterozygosity (LOH) 
analysis demonstrated that in one of the pheochromocytomas, reduction to 
homozygosity was observed for both 17p and 17q markers while the adrenal 
cortical tumor demonstrated LOH for only 17q markers. The frequent LOH 
surrounding the NF1 locus and lack of neurofibromin expression in these tumors 
suggest that NF1 gene mutations may contribute to the development of adrenal 
gland neoplasms in patients with NF1.