Imaging features of benign and malignant ampullary and periampullary lesions.

The ampulla of Vater is an important anatomic landmark where the common bile duct and main pancreatic duct converge in the major duodenal papilla. Imaging evaluation of the ampulla and periampullary region poses a unique diagnostic challenge to radiologists because of the region's complex and variable anatomy and the variety of lesions that can occur. Lesions intrinsic to the ampulla and involved segment of the biliary tree can be neoplastic, inflammatory, or congenital. Neoplastic lesions include ampullary adenocarcinomas and adenomas, which often are difficult to differentiate, as well as pancreatic or duodenal adenocarcinomas, pancreatic neuroendocrine tumors, and cholangiocarcinomas. Ultrasonography (US), computed tomography, magnetic resonance (MR) imaging, and MR cholangiopancreatography are commonly used to evaluate this region. Endoscopic retrograde cholangiopancreatography or endoscopic US examination may be necessary for more definitive evaluation. Periampullary conditions in the duodenum that may secondarily involve the ampulla include neoplasms, duodenitis, duodenal diverticula, and Brunner's gland hyperplasia or hamartomas. Because these lesions can exhibit a wide overlap of imaging features and subtle or nonspecific imaging findings, diagnosis is made on the basis of patient age, clinical history, and imaging and laboratory findings. Given the complexity of imaging evaluation of the ampulla and periampullary region, it is essential for radiologists to understand the variety of lesions that can occur and recognize their imaging characteristics.

Case Report: Metastasis of a Trigeminal Malignant Peripheral Nerve Sheath Tumor to the Corpus Callosum.

BACKGROUND AND IMPORTANCE: Malignant peripheral nerve sheath tumors (MPNST) are relatively rare tumors of peripheral nerves that are notable for their locally aggressive nature, ability to metastasize, poor prognosis, and association with Neurofibromatosis type I. We present the case of a patient with a trigeminal nerve MPNST who developed an unusual metastasis to the corpus callosum, in the absence of any other central nervous system or systemic metastatic disease. We review the pathology and presentation of MPNST. CLINICAL PRESENTATION: A 53-yr-old woman presented with a 1-yr history of paroxysmal facial pain and dysesthesias in the right V1 and V2 distributions of the trigeminal nerve. She was initially diagnosed with trigeminal neuralgia although further imaging showed a cavernous sinus mass extending along the trigeminal nerve. She later developed an isolated lesion in the corpus callosum that was biopsied and consistent with MPNST. CONCLUSION: This case reviews the pathology and aggressive nature of MPNST and demonstrates an unusual site of metastasis. Clinicians should remain aware that MPNST can metastasize to sites in the central nervous system as well as systemically. Furthermore, clinicians should have a high index of suspicion for secondary causes of trigeminal neuralgia in cases with atypical features.