Malignant schwannoma in siblings with neurofibromatosis.

Three brothers with neurofibromatosis (NF) died of sarcoma. The proband tumor had malignant schwannoma. The histologic nature of the sarcoma in the other two brothers was not known, but it seemed likely to be similar to that of the proband. However, the sarcomatous lesions in these two siblings developed in the patients' right lower limbs which showed clinical and radiological evidence of anterior bowing of the tibia. Their mother and two other siblings have neurofibromatosis, but have not developed malignant tumors. The unaffected father died at age 61 of carcinoma of the common bile duct. An unaffected sister developed adenocarcinoma of both colon and lung. Although it is known that patients with NF are at a high risk of developing malignant sarcoma and second primary malignancies, it is not clear whether this association is genetically determined. The family we report has some of the features of a "cancer family" and suggests that sarcomatous transformation in patients with NF may be genetically influenced. This report raises the possibility that the presence of congenital malformation and exposure to irradiation may predispose patients with neurofibromatosis to develop malignant schwannoma.