Validation of combined carcinoembryonic antigen and glucose testing in pancreatic cyst fluid to differentiate mucinous from non-mucinous cysts

Pancreas Cyst Diagnosis and Advances in Cyst Fluid Analysis

Pancreatic Cystic Neoplasms (PCN) represent a diverse group of tumors, some of which may progress to pancreatic cancer. Considering their high prevalence in the general population, the development of reliable biomarkers is crucial. The ideal biomarker will accurately diagnose the subtype of PCN and assess the risk of high-grade dysplasia or invasive cancer. Cyst fluid analysis has emerged as a promising approach to accomplish this goal, yet no single marker has yet gained unanimous support for routine inclusion in PCN evaluation.

Evaluating Carcinoembryonic Antigen and Glucose Levels in Pancreatic Cyst Fluid for Mucinous Versus Non-mucinous Differentiation

BACKGROUND

A more precise identification of mucinous cysts will lower the likelihood of needless pancreatic surgery. Pancreatic cyst fluid (PCF) contains glucose and carcinoembryonic antigen (CEA), which serve as biomarkers to differentiate mucinous from non-mucinous pancreatic cystic neoplasms (PCNs).

OBJECTIVE

To evaluate the diagnostic accuracy of combined CEA and glucose levels in PCF for distinguishing mucinous from non-mucinous PCNs preoperatively.

METHODS

After receiving approval from the Institutional Ethical Committee of Indira Gandhi Institute of Medical Sciences, Patna, a cross-sectional validation research was carried out. All patients ≥18 years of age who had undergone pancreatic surgery or endoscopic ultrasound-guided fine-needle aspiration (EUS-FNA) for a pancreatic cystic lesion and for whom PCF was acquired were eligible for inclusion. Patients were excluded if there was no PCF available, if they had been diagnosed with an extrapancreatic illness (such as ampullary adenoma), or if they could not be excluded due to pancreatic cancer generated from PCN. Diagnoses were pathologically confirmed. We performed measurements for CEA and glucose in PCF. CEA and glucose were measured using an Architect i2000SR analyzer (Abbott, Lake County, IL) and AU 5800 Beckman Coulter (Brea, CA), respectively. Diagnostic accuracy was evaluated by receiver operator characteristic (ROC) curves.

RESULTS

PCF was obtained from 100 patients, of whom 54 (54%) had mucinous PCN and 46 (46%) had non-mucinous PCN. When CEA (cut-off ≥ 151 ng/ml) and glucose levels (cut-off ≤ 50 mg/dL) were combined, the results showed 46% sensitivity and 92% specificity. However, when CEA (cut-off ≥ 17 ng/ml) or glucose testing (cut-off ≤ 50 mg/dL) was used separately, the results showed 82% sensitivity and 73% specificity.

CONCLUSION

The combined CEA and glucose testing in PCF demonstrated high specificity and sensitivity for differentiating mucinous from non-mucinous PCNs, suggesting its potential utility in preoperative diagnosis.

Endoscopic ultrasound-guided fine-needle aspiration for pancreatic cystic lesions: a comprehensive review

Advancements in diagnostic radiology have amplified the incorporation of these techniques into routine clinical practice. Concurrently, the frequency of incidentally identifying pancreatic cystic lesions (PCLs) has surged. PCLs encompass diverse categories contingent upon their origin. Among them, branch duct-intraductal papillary mucinous neoplasms (BD-IPMN) and mucinous cystic neoplasms (MCN) are categorized as mucinous cystic lesions that have malignant potential. Even solid neoplasms occasionally show cystic degeneration. Therefore, precise differential PCL diagnosis is crucial to optimize clinical management strategies and detect malignant transformations. Endoscopic ultrasound (EUS) affords comprehensive visualization of the pancreas with high-resolution ultrasound, complemented by fine-needle aspiration (FNA) under real-time EUS guidance, which is a minimally invasive procedure for obtaining pathological samples. This synergy has established EUS and EUS-FNA as vital procedures in the management of PCLs, enabling differentiation of PCLs. Cyst fluid analysis has played a pivotal role in deciding the optimal management strategy. The efficacy of cytological analysis is limited by scant cytologic material. The "string sign" test evaluates fluid viscosity, and its simplicity warrants initial consideration. Amylase and tumor markers, such as CEA, have been studied, but they yield varied sensitivity and specificity. Glucose and genetic mutations (KRAS, GNAS) exhibit promise, while comprehensive genomic profiling underscores genetic insights. Through-the-needle biopsy and needle-based confocal laser endomicroscopy also show high diagnostic yield. EUS-FNA, however, entails risks like infection and needle tract seeding, emphasizing the need for proper utilization. Pancreatic cyst fluid analysis augments diagnostic accuracy and informs clinical decisions, making it a valuable adjunct to imaging.

Neutrophil Gelatinase-Associated Lipocalin for the Differentiation of Mucinous Pancreatic Cystic Lesions

Undetermined pancreatic cystic lesion (PCL) differentiation benefits from endoscopic ultrasound (EUS) based on morphology and cyst fluid analysis, but room for new biomarkers exists. Our aim was to assess the intracystic and serum diagnostic value of neutrophil gelatinase-associated lipocalin (Ngal) and interleukin 1 beta (IL-1β) for differentiation of PCLs. This prospective study included patients from one tertiary hospital, evaluated between April 2018 and May 2020. EUS fine-needle aspiration or pancreatic pseudocysts drainage was the source of PCL intracystic liquid. The final diagnosis was based on surgery or EUS results (morphology, cytology, glucose, and CEA-carcinoembryogenic antigen). The intracystic samples were tested for Ngal, IL-1β, glucose, and CEA, and serum for Ngal and IL-1β. We evaluated 63 cysts, 33 pseudocysts, and 30 non-inflammatory cysts. The diagnostic sensitivity and specificity for mucinous PCL was 70.8% and 92.3% for intracystic Ngal (cut-off: 500-800 ng/dL), without correlation with serum Ngal, no matter the inclusion of infected pseudocysts. After exclusion of infected pseudocysts, the sensitivity and specificity for glucose were 87% and 75%, respectively, and for CEA, they were 87.1%, and 96.8%, respectively. Intracystic Ngal shows promise in differentiating mucinous PCLs, but researchers need to conduct further studies to confirm its effectiveness. Intracystic IL-1β and serum Ngal made no diagnostic contribution.

Revisiting the performance of cyst fluid carcinoembryonic antigen as a diagnostic marker for pancreatic mucinous cysts: a comprehensive 20-year institutional review

OBJECTIVE

Elevated pancreatic cyst fluid carcinoembryonic antigen (CEA) has been routinely used to classify mucinous cysts. This study incorporates original data that established the CEA ≥192 ng/mL threshold with over 20 years of additional data and reassesses the diagnostic performance of CEA for differentiating mucinous from non-mucinous cysts.

DESIGN

1169 pancreatic cysts (1999-2021) with CEA results were identified. 394 cases had histological confirmation as the diagnostic standard. Additionally, 237 cysts without histological confirmation demonstrated KRAS, GNAS, or RNF43 mutations by molecular testing and were combined with the histologically confirmed cysts for separate analysis on a total cohort of 631 cysts.

RESULTS

Median CEA was significantly higher in mucinous cysts (323.9 ng/mL, n=314) versus non-mucinous cysts (204.6 ng/mL, n=80) (p<0.001). Receiver operating characteristic curve analysis demonstrated an optimal CEA cut-off of 20 ng/mL (area under the curve: 80%), though the specificity was lower than desired (sensitivity 89%, specificity 64%). At the previously established threshold of 192 ng/mL, sensitivity and specificity were 56% and 78%, respectively. To achieve a specificity of 85% as originally reported, a CEA threshold of 250 ng/mL was needed; the 13 false positive cases at this threshold included 4 benign simple cysts, 2 squamoid cysts, 1 serous cystadenoma, 1 lymphoepithelial cyst and 5 more uncommon entities. All results remained similar within the total cohort after including additional cases with KRAS/GNAS/RNF43 mutations only.

CONCLUSION

Cyst fluid CEA continues to be a useful test in the diagnosis of mucinous pancreatic cysts but does not appear as specific as previously reported. Raising the CEA threshold to 250 ng/mL to maintain specificity for differentiating mucinous from non-mucinous cysts may be considered.