Cervicothoracic malignant peripheral nerve sheath tumor in a 12-year-old girl with neurofibromatosis type 1.

We encountered a 12-year-old girl with neurofibromatosis type 1 (NF1) who developed a low-grade cervicothoracic malignant peripheral nerve sheath tumor (MPNST). Computed tomography of the neck showed an elastic firm tumor measuring 7 x 6 x 4 cm and arising from the upper mediastinum. She had no pain or neurological symptoms, but the tumor enlarged to ca. 8 x 8 x 4 cm over the following 7 months. Although we had diagnosed a neurofibroma by preoperative incisional biopsy, the resected tumor showed low-grade MPNST in the central portion of the tumor. In treating a tumor in a patient with NF1, we must recognize that partial biopsies do not necessarily establish a definitive diagnosis and that a growing tumor may indicate malignant transformation.