Morphological and functional investigations of neuroendocrine tumors of the pancreas

Abstract

Neuroendocrine tumors of the pancreas are rare neoplasms arising predominantly from the pancreatic islets of Langerhans and are thus known as islet cell tumors. More than the half of all neuroendocrine tumors are called functioning islet cell tumors because they secrete one or more biologically active peptides that may produce clinical symptoms. Clinical diagnosis of non-functioning, i.e., biologically inactive, tumors is often delayed and patients tend to present with advanced tumors (size greater than 5 cm) that are easily localized by using conventional imaging modalities. On the other hand, symptoms of functioning islet cell tumors usually appear early in the clinical course, rendering the preoperative localization of these small hormone-producing tumors (size less than 2 cm) difficult with non-invasive methods. Since functioning islet cell tumors can often be cured by surgical resection, invasive procedures are warranted when necessary for localization diagnosis. Failure to search for, detect, and resect these small tumors will invariably result in persistent symptoms. Regarding the unsatisfactory results of morphological imaging methods, functional studies, especially arterial stimulation with hepatic venous samplings, may provide a preoperative regionalization of the pancreatic adenoma, regardless of its size.

ENETS Consensus Guidelines for the Management of Peritoneal Carcinomatosis from Neuroendocrine Tumors

“…With this in mind, with both pre- and intraoperative explorations, particular attention should be given to the right and left subdiaphragmatic spaces, the small and great omentum (especially in patients who have small intestinal GEP tumors), lateral abdominal spaces close to the colon, mesenteric vessels and pelvis (pouch of Douglas). In patients with small bowel obstruction, which may be secondary to the primary tumor, peritoneal nodules and/or associated mesenteric retraction, entero-CT scan or entero-MRI may be useful in both diagnosis and therapeutic planning [13,17,18,20,24,25,26,27]. …”

Well-Differentiated Pancreatic Nonfunctioning Tumors/Carcinoma

“…Fifty-nine percent to 80% of the patients present with synchronous liver metastases at diagnosis [10, 25]. Given the mostly large primary (>5 cm), localizing the tumor at the head of the pancreas, followed by the body and tail, is straightforward [26]. …”

Contrast enhancement pattern on multidetector CT predicts malignancy in pancreatic endocrine tumours

“…In fact, previous studies reporting on pNET characteristics at MDCT have demonstrated that benign tumours are usually small, showing a homogenous hypervascular pattern after contrast injection followed by early wash-out in the venous phase. On the contrary, larger pNETs have a less homogeneous CEP and are associated with greater malignant potential, especially in the presence of necrosis and calcifications [19][20][21][22]. From a practical point of view, however, when obvious markers of malignancy are lacking, preoperative anticipation of tumour grade in pNETs is based on tumour size.…”

“…In the evaluation of pNETs, imaging plays a pivotal role for suggesting the best therapeutic approach, allowing the localization of functioning neoplasms, the differential diagnosis with respect to other pancreatic tumours or non-tumoral pancreatic masses [21], the identification of signs of malignancy and the local and distant staging [21][22][23]. The novel finding provided by our study is represented by the fact that CEP of pNETs, as defined during a standardized multiphasic MDCT study, even if conducted by using scanners of different generations, provides information matching all histological parameters of prognostic relevance and could therefore be used to predict the course of pNETs.…”