Pancreatic neuroendocrine neoplasms (panNENs) are heterogeneous neoplasms with neuroendocrine differentiation that show characteristic clinical, histomorphologic, and prognostic features; genetic alterations; and biologic behavior. Up to 10% of panNENs develop in patients with syndromes that predispose them to cancer, such as multiple endocrine neoplasia type 1, von Hippel-Lindau disease, tuberous sclerosis complex, neurofibromatosis type 1, and glucagon cell adenomatosis. PanNENs are classified as either functioning tumors, which manifest early because of clinical symptoms related to increased hormone production, or nonfunctioning tumors, which often manifest late because of mass effect. PanNENs are histopathologically classified as well-differentiated pancreatic neuroendocrine tumors (panNETs) or poorly differentiated pancreatic neuroendocrine carcinomas (panNECs) according to the 2010 World Health Organization (WHO) classification system. Recent advances in cytogenetics and molecular biology have shown substantial heterogeneity in panNECs, and a new tumor subtype, well-differentiated, high-grade panNET, has been introduced. High-grade panNETs and panNECs are two distinct entities with different pathogenesis, clinical features, imaging findings, treatment options, and prognoses. The 2017 WHO classification system and the eighth edition of the American Joint Committee on Cancer staging system include substantial changes. Multidetector CT, MRI, and endoscopic US help in anatomic localization of the primary tumor, local-regional spread, and metastases. Somatostatin receptor scintigraphy and fluorine 18fluorodeoxyglucose PET/CT are helpful for functional and metabolic assessment. Knowledge of recent updates in the pathogenesis, classification, and staging of panNENs and familiarity with their imaging findings allow optimal patient treatment. © RSNA, 2020 • radiographics.rsna.org

Hereditary gastrointestinal (GI) cancer syndromes due to specific germline mutations are characterized by an increased risk of GI tract malignancies, extra-GI tract cancers, and benign abnormalities. These syndromes include Lynch syndrome, familial adenomatous polyposis, juvenile polyposis syndrome, Peutz-Jeghers syndrome, Cowden syndrome, hereditary diffuse gastric cancer, and hereditary pancreatic cancer. Timely identification of the responsible genes will help predict future cancer risks in these patients and their family members. Early detection of cancers is possible with appropriate screening methods; risk-reducing measures will help in cancer prevention. Select malignancies and benign conditions associated with these syndromes have distinctive imaging features that can aid in classifying the syndromes. Imaging also plays a pivotal role in screening and surveillance of patients as well as their at-risk relatives and is invaluable for follow-up of treated malignancies. The American College of Gastroenterology has established specific guidelines for diagnosis and management of hereditary GI cancer syndromes. Knowledge of the imaging features of various pathologic conditions and screening strategies will guide appropriate management of patients and at-risk family members. ©

Roy [1881], who first observed rhythmic contractions of the spleen, distinguished between two types; he says, "I will speak of that which is proper to the spleen and which has no relation to changes in the height of the blood-pressure, as the specific splenic rhythm, while that which occurs in conjunction with the Trau b e -He ring blood-pressure curves will be referred to as the Traube-Hering splenic rhythm." The first distinction which Roy makes is in the period of the rhythm, the socalled specific splenic waves having a slower rhythm than the TraubeHering splenic waves. While it is not explicitly stated, the inference from Roy's paper is that the specific splenic waves are of longer than 60 sec. duration, while the Traube-Hering splenic waves are shorter. We have found, however, that the shorter splenic waves (under 50 sec.) sometimes occur (Fig. 1 a) and sometimes do not (Fig. 1 b) in conjunction with the undulatory blood-pressure waves, while sometimes the longer splenic waves (over 60 sec.) are accompanied by undulatory bloodpressure waves as shown in Fig. 1 c. Below (Table I) will also be found instances in which both rhythms were observed coincident with one another when the period was over 60 sec., and others in which the blood-pressure rhythms were absent when the period of the splenic rhythm was under 50 sec.The question therefore is: are these two splenic rhythms essentially different in character, or, the splenic waves being of the same character in both cases, are there reasons why the blood-pressure should fluctuate in one case and not in the other?In different experiments we have brought about the activity of the spleen in various ways, but each type of stimulus may provoke a splenic rhythm either with or without fluctuations in the blood-pressure.

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