Application of Contrast-Enhanced Ultrasound in the Diagnosis of Solid Pseudopapillary Tumors of the Pancreas: Imaging Findings Compared With Contrast-Enhanced Computed Tomography

Role of contrast-enhanced ultrasound with time-intensity curve analysis for differentiating hypovascular solid pancreatic lesions

OBJECTIVES

To evaluate the clinical value of contrast-enhanced ultrasound (CEUS) with time-intensity curve (TIC) in distinguishing different types of hypovascular solid pancreatic lesions.

METHODS

A total of 89 patients with 90 pancreatic lesions (all confirmed by surgery or biopsy pathology) that manifested hypoenhancement on contrast-enhanced ultrasound (CEUS) were included in this study. Six peak enhancement patterns were proposed for differentiating hypovascular pancreatic lesions. CEUS qualitative and TIC-based quantitative parameters were analyzed, and each lesion was scored based on the statistically significant qualitative parameters to evaluate the diagnostic ability of CEUS for hypovascular solid pancreatic lesions.

RESULTS

Qualitative parameters such as peak enhancement pattern II/III/IV, penetrating vessels, centripetal enhancement, and early washout were reliable indicators of malignant lesions, and lesions scored based on these qualitative parameters, with a score ≥ 2, were highly suspected to be malignant lesions. Pattern I had an accuracy of 83.33% for predicting mass-forming pancreatitis (MFP), pattern V had an accuracy of 96.67% for predicting solid pseudopapillary tumors of the pancreas (SPTP), and pattern VI had an accuracy of 81.11% for predicting neuroendocrine tumors/carcinomas (NETs/NECs). For quantitative analysis, nodule/pancreatic parenchyma echo intensity reduction ratio was significantly greater in malignant lesions.

CONCLUSIONS

CEUS qualitative and TIC-based quantitative parameters have clinical value in distinguishing malignant from benign hypovascular pancreatic lesions.

KEY POINTS

• Contrast-enhanced ultrasound helps clinicians assess patients with pancreatic lesions. • Six peak enhancement patterns are proposed for differentiating pancreatic hypovascular lesions. • Qualitative parameters such as peak enhancement pattern II/III/IV, penetrating vessels, centripetal enhancement, early washout, and quantitative parameter nodule/pancreatic parenchyma echo intensity reduction ratio were important characteristics to discriminate malignant from hypovascular benign lesions.

Differential diagnosis between pancreatic solid pseudopapillary tumors and pancreatic neuroendocrine tumors based on contrast enhanced ultrasound imaging features

PURPOSES

To evaluate the application of contrast enhanced ultrasound (CEUS) in preoperatively differential diagnosis between pancreatic solid pseudopapillary tumors (SPTs) and pancreatic neuroendocrine tumors (pNETs).

PATIENTS AND METHODS

This retrospective study was approved by Institutional Review Board. Patients with surgical resection and histopathological diagnosis as SPTs and pNETs were included. All patients underwent B mode ultrasound (BMUS) and CEUS examinations within one week before surgical operation. On BMUS, the size, location, echogenicity, calcification, and margin of lesions were observed and recorded. On CEUS imaging, enhancement patterns, and enhancement degrees were recorded and analyzed. An independent t-test or Mann-Whitney U test was used for comparison between continuous variables. Chi-square test was used to compare the CEUS patterns.

RESULTS

From February 2017 to Dec 2022, patients diagnosed as SPTs (n = 39) and pNETs (n = 48) were retrospectively included. On BMUS, anechoic cystic changes (19/39, 48.72%) and hyperechoic calcification (14/39, 35.90%) are more commonly detected in SPTs (P = 0.000). On CEUS imaging, the majority of SPTs (27/39, 69.23%) showed hypo-enhancement in the arterial phase, while most of the pNETs (36/48, 75.00%) showed hyper- or iso-enhancement in the arterial phase (P = 0.000). In the venous phase, most of the SPTs (32/39, 82.05%) showed hypo-enhancement, while over half of pNETs (29/48, 60.42%) showed hyper- or iso-enhancement compared to pancreatic parenchyma (P = 0.001).

CONCLUSIONS

CEUS is a valuable and non-invasive imaging method to make preoperatively differential diagnoses between SPTs and pNETs.

Solid Pseudopapillary Neoplasm of the Pancreas: Unfolding an Intriguing Condition

Pancreatic cancer is one of the most lethal malignant neoplasms, with a 1-year survival rate after diagnosis of 24%, and a 5-year survival rate of only 9%. While this illustrates the behavior of its main histologic type - ductal adenocarcinoma, there are other histologic subtypes of pancreatic cancer that can harbor excellent prognosis. Solid pseudopapillary neoplasm, described as a rare low-grade malignant neoplasm by the World Health Organization, is the best example of that, having an overall 5-year survival rate of about 97%. Not only the prognosis, but everything about this entity is unique: its histogenesis, epidemiology, presentation, imaging characteristics, cytology features, immunohistochemical profile, and treatment. This explains the urge to improve our understanding about this entity and thus our ability to accurately recognize and manage it. Having this in mind, this article aims to summarize the most relevant topics regarding this entity.

Clinical value of contrast-enhanced ultrasound enhancement patterns for differentiating solid pancreatic lesions

OBJECTIVES

To explore the diagnostic value of contrast-enhanced ultrasound (CEUS) enhancement patterns for differentiating solid pancreatic lesions and compare them with conventional ultrasound (US) and enhanced computed tomography (CT).

METHODS

A total of 210 patients with solid pancreatic lesions who had definite pathological or clinical diagnoses were enrolled. Six CEUS enhancement patterns were proposed for solid pancreatic lesions. Two US doctors blindly observed the CEUS patterns of solid pancreatic lesions and the interrater agreement was analyzed. The diagnostic value of CEUS enhancement patterns for differentiating solid pancreatic lesions was evaluated, and the diagnostic accuracy was compared with that of US and enhanced CT.

RESULTS

There was good concordance for six CEUS enhancement patterns of solid pancreatic lesions between the two doctors, with a kappa value of 0.767. Hypo-enhancement (Hypo-E) or centripetal enhancement (Centri-E) as the diagnostic criteria for pancreatic carcinoma had an accuracy of 87.62%; hyper-enhancement (Hyper-E) for neuroendocrine tumors had an accuracy of 92.89%; capsular enhancement with low or uneven enhancement inside the tumor (Capsular-E) for solid pseudopapillary tumors had an accuracy of 97.63%; and iso-enhancement (Iso-E) or iso-enhancement with focal hypo-enhancement (Iso-fhypo-E) for focal pancreatitis had an accuracy of 89.10%. The diagnostic accuracy of CEUS was significantly different from that of US for 210 cases of solid pancreatic lesions (p < 0.05) and was not significantly different from that of enhanced CT for 146 cases of solid pancreatic lesions (p > 0.05).

CONCLUSIONS

The different enhancement patterns of solid pancreatic lesions on CEUS were clinically valuable for differentiation.

KEY POINTS

• Six CEUS enhancement (E) patterns, including Hyper-E, Iso-E, Iso-fhypo-E, Hypo-E, Centri-E, and Capsular-E, are proposed for the characterization of solid pancreatic lesions. • Using Hypo-E or Centri-E as the diagnostic criteria for pancreatic carcinoma, Hyper-E for neuroendocrine tumors, Capsular-E for solid pseudopapillary tumors, and Iso-E or Iso-fhypo-E for focal pancreatitis on CEUS had relatively high diagnostic accuracy. • The diagnostic accuracy of CEUS was greatly increased over that of US and was not different from that of enhanced CT.

Pancreatic neuroendocrine tumours: spectrum of imaging findings

Pancreatic neuroendocrine tumours (pNETs) are rare and heterogeneous group of neoplasms presenting with a wide variety of symptoms and biological behaviour, from indolent to aggressive ones. pNETs are stratified into functional or non-functional, because of their ability to produce metabolically active hormones. pNETs can be an isolate phenomenon or a part of a hereditary syndrome like von Hippel-Lindau syndrome or neurofibromatosis-1. The incidence has increased in the last years, also because of the improvement of cross-sectional imaging. Computed tomography (CT), magnetic resonance imaging (MRI) and functional imaging are the mainstay imaging modalities used for tumour detection and disease extension assessment, due to easy availability and better contrast/spatial resolution. Radiological imaging plays a fundamental role in detection, characterization and surveillance of pNETs and is involved in almost every stage of patients' management. Moreover, with specific indications and techniques, interventional radiology can also play a role in therapeutic management. Surgery is the treatment of choice, consisting of either partial pancreatectomy or enucleation of the primary tumour. This article reviews the radiologic features of different pNETs as well as imaging mimics, in order to help radiologists to avoid potential pitfalls, to reach the correct diagnosis and to support the multidisciplinary team in establishing the right treatment.