Cystic Pancreatic Neuroendocrine Tumor in a Patient with Neurofibromatosis Type 1

Neurofibromatosis type 1 (NF-1) is strongly associated with neurofibromas and malignancies. Solid pancreatic neuroendocrine tumors (PanNETs) have been recently reported in patients with NF-1. PanNETs are always solid and rarely present with a cystic appearance due to central necrosis and hemorrhage caused by rapid growth. A 33-year-old female diagnosed with NF-1 at age 16 was referred for evaluation of a pelvic mass found on abdominal ultrasound. Magnetic resonance imaging showed a 6 cm solid pelvic mass adjacent to the left external iliac artery, and contrast-enhanced computed tomography scan showed a 3-cm solid para-aortic mass and a 3-cm cystic mass in the pancreatic tail. Endoscopic ultrasonography showed a cystic tumor with necrotic tissue and septa. Preoperative diagnosis was pancreatic cystic malignancy with para-aortic lymph node metastasis accompanied with a pelvic neurofibroma. These lesions were resected simultaneously. The specimen resected from the pancreas showed a necrotizing cystic tumor invading abutting lymph nodes. Immunohistochemical analysis showed positive chromogranin A and synaptophysin. The Ki-67 index was <1%, and the mitotic count was 1/10 in high power field. Therefore, a non-functional PanNET (grade G1) was diagnosed. The pelvic and para-aortic tumors were both neurofibromas. A cystic appearance is atypical for PanNET and makes preoperative diagnosis difficult. To the best of our knowledge, this is the first report of a cystic PanNET in a patient with NF-1.