Diagnostic yield and safety of pancreatic cystic lesions: A comparison between EUS-FNA and EUS-FNB

Abstract

Objective

In recent years, the incidence and detection rate of pancreatic cystic lesions (PCLs) have increased significantly. Endoscopic ultrasound (EUS) plays an indispensable role in the diagnosis and differential diagnosis of PCLs. However, evidence comparing the diagnostic performance of EUS-guided fine-needle aspiration (EUS-FNA) and fine-needle biopsy (FNB) remains limited. This study aims to compare the diagnostic yield, adequacy of tissue acquisition, and safety between EUS-FNA and EUS-FNB in evaluating PCLs to inform clinical practice.

Methods

A retrospective review was conducted on patients with PCLs who underwent either EUS-FNA or EUS-FNB between January 2014 and August 2021. The diagnostic yield, tissue acquisition adequacy, and incidence of adverse events were compared between the 2 groups.

Results

A total of 90 patients with PCLs were included (52 in the FNA group and 38 in the FNB group). The diagnostic yield was similar between the FNA and FNB groups (94.2% vs 94.7%, P>0.05). The adequacy of tissue acquisition was 71.2% in the FNA group and 81.6% in the FNB group (P>0.05). No statistically significant difference was observed in the incidence of adverse events between the 2 groups (P>0.05).

Conclusion

Both EUS-FNA and EUS-FNB demonstrate equally high diagnostic yields and tissue adequacy in PCLs, with excellent safety profiles. Both methods are safe and effective diagnostic tools for evaluating PCLs.

The incidence of pancreatic cystic lesions (PCLs) in the general population is about 2.5% and progressively increases with age^[1-2]. A subset of PCLs has malignant potential and surgical resection is the only effective means^[3]. But the annual risk of asymptomatic PCLs progressing to cancer was only 0.47% for 7 years^[4]. Surgical resection or frequent monitoring of low-risk PCLs may place a huge burden on patients. Therefore, it is critical to accurately identify PCLs that require surgery or monitoring.

As imaging technology improves by leaps and bounds, the detection rate of PCLs is increasing with 2.6% by computed tomography (CT) and 13.5% to 19.6% by magnetic resonance imaging (MRI)^[5-6]. Despite the increased detection rate of CT and MRI for PCLs, making a differential diagnosis remains challenging. It may lead to misdiagnosis and inappropriate treatment (i.e., unnecessary surgery of benign lesions or lack of surveillance of potentially malignant lesions).

Compared with CT or MRI, endoscopic ultrasound (EUS) harbors a powerful local resolution capability and plays a crucial role in differentiating diagnosis of PCLs^{[4, 7]}. EUS-guided fine-needle aspiration (EUS-FNA) is recommended for cystic fluid analysis and pathological examination to help the diagnosis of PCLs when the diagnosis is unclear and the diagnosis result may change the treatment^[8]. However, FNA has several limitations: It obtains less tissues, and diagnostic accuracy is largely dependent on rapid diagnosis by cytopathologists^[9-11].

To overcome these limitations, a new fine needle biopsy (FNB) device has been designed, it can obtain more tissues and reduce the number of punctures^[12]. The diagnostic performance of EUS-FNB is superior to that of EUS-FNA in pancreatic solid lesions, but current studies have rarely focused on the role of FNB in PCLs. And there is a lack of comparative studies on the diagnostic performance of EUS-FNA and EUS-FNB in PCLs. This study aims to compare the specimen adequacy, diagnostic yield, and safety of EUS-FNA and EUS-FNB in PCLs, and to provide guidance for future needle type selection.

1. Patients and methods

1.1. Ethics declaration

This retrospective study was approved by the Ethical Committee (No. R22118) and the requirement for informed consent was waived.

1.2. Patients

From January 2014 to August 2021, patients with suspected PCLs by CT or MRI who subsequently underwent EUS-FNA or EUS-FNB at the Department of Gastroenterology, Third Xiangya Hospital of Central South University, were enrolled in this study. According to the inclusion criteria, 90 patients were eventually enrolled (Figure 1). The inclusion criteria were as follows: 1) CT/MRI showed PCLs; 2) EUS-FNA or EUS-FNB was performed; 3) sufficient cyst fluid was obtained for analysis; 4) cytological or histological examination was implemented. Exclusion criteria: Patients lacking the results of cystic fluid amylase, carcinoembryonic antigen (CEA), or carbohydrate antigen (CA19-9).

Figure 1. Study flowchart.

PCLs: Pancreatic cystic lesions; CT: Computed tomography; MRI: Magnetic resonance imaging; EUS: Endoscopic ultrasound; EUS-FNA: EUS-guided fine-needle aspiration; EUS-FNB: EUS-guided fine-needle biopsy; CEA: Carcinoembryonic antigen; CA19-9: Carbohydrate antigen 19-9.

1.3. EUA-FNA or EUS-FNB procedure

All EUS was using a curved linear array echoendoscope (ME2 PLUS, Olympus Medical Systems, Tokyo, Japan or SU9000, Fujifilm Medical Systems, Tokyo, Japan) to evaluate the PCLs based on their location, size, and characteristic features (mural nodules, communication with pancreatic duct, dilatation of pancreatic duct, etc.).

After assessing the regional blood flow, the needle with a stylet was advanced into the target lesion under EUS guidance. A 22G needle in the EUS-FNA group (Boston Scientific Corporation, Natick, MA, USA) was employed for gastric or duodenal puncture, compared to a 22G ProCore needle (Cook EchoTip ProCore) in the FNB group. After aspiration of the cyst fluid as much as possible, puncture was performed on the collapsed cyst wall or solid part. The obtained cyst fluid was devoted to biochemical analysis (total amylase and pancreatic amylase) and tumor marker determination (CEA and CA19-9), while the acquired tissues were processed for cytopathological or histopathological examination (Figure 2).

Figure 2. Procedures of EUS-FNA and EUS-FNB.

A: Cystic fluid obtained by EUS-FNA or EUS-FNB; B: Specimen obtained by EUS-FNA; C: Specimen obtained by EUS-FNB; D: EUS-guided biopsy from PCLs using FNA; E: EUS-guided biopsy from PCLs using FNB.

1.4. Final diagnosis

For patients who underwent surgery, the final diagnosis was based on the definite histological diagnoses obtained from the surgically resected specimens. For patients who did not undergo surgery, the diagnosis was made using the following methods based on the relevant studies: 1) The diagnosis was considered definitive when histological examination obtained through EUS-FNA or EUS-FNB was diagnostic for malignancy or for benign disease and clinical/imaging manifestations consistent with it. 2) In case of an inconclusive diagnosis at EUS-FNA or EUS-FNB and no surgical specimen was available, a committee of 3 endoscopists and 2 pathologists nonblindedly reviewed all available information, including clinical presentation, CT/MRI, EUS morphology, biochemical analysis and tumor markers of cyst fluid, cytology or histology to make a consensus diagnosis, and these patients were closely followed for 6 months^[13-15]. Patients without a final consensus diagnosis were excluded from the study.

1.5. Outcome measurements

The diameter of the cyst was defined as the longest axis of the lesion under the EUS. True cysts, pseudocysts, serous cystadenomas (SCAs), mucinous cystadenomas (MCNs), intraductal papillary mucinous neoplasms (IPMNs) (with or without mild to moderate dysplasia), and autoimmune pancreatitis were considered as benign PCLs. Cystadenocarcinoma, intraductal papillary mucinous carcinoma (including intraductal papillary myxoma with severe dysplasia), solid pseudopapillary tumor, and pancreatic cancer were regarded as malignant PCLs.

The primary outcome embodied diagnostic accuracy, sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV). The secondary outcomes were the specimen adequacy and adverse events. The specimen adequacy was divided into 6 grades in accordance with the method proposed by Gerke, et al^[16-17]. In this method, score 0 was defined as no cells or tissues obtained, score 1-2 referred to admission of cytological examination but prohibition of histological examination in order to access specimens, score 3-5 meant histological examination was allowed, and score 4-5 was considered to have obtained sufficient tissues for diagnosis.

Adverse events included intra-cystic or extra-cystic bleeding, infection, acute pancreatitis, etc. Intra-cystic or extra-cystic bleeding was defined as active bleeding inside the cyst as a spurting vessel enhanced by color-Doppler, or a cystic lesion that progressively increases in size after evacuation, with change in morphological aspect from anechoic to hyperechoic PCLs^[18]. Infection was defined as a body temperature exceeding 38 ℃ in the absence of other etiologies. Acute pancreatitis was defined as persistent upper abdominal pain associated with elevated pancreatic enzymes at least 3 times the upper limit of normal following EUS-FNA or EUS-FNB^[18].

1.6. Statistical analysis

All data were analyzed by SPSS 23.0 version statistical software. Normally distributed continuous variables were expressed as mean±standard deviation ( $\overline{x}$ ±s), while the abnormally distributed continuous variables were expressed as median (first quartile, third quartile), and categorical variables as quantity (percentage). Chi-square test or Fisher exact test was implemented for categorical variables, and independent sample t-test was used for continuous variables. A P<0.05 was considered statistically significant.

2. Results

2.1. Patients and cyst characteristics

A total of 90 patients (41 females and 49 males, 52 in a FNA group and 38 in a FNB group) with PCLs (including cystic lesions with solid components) who underwent EUS-FNA or EUS-FNB were enrolled after excluding 31 patients from whom did not undergo EUS-FNA/FNB, failed to obtain sufficient cyst fluid for biochemical or tumor marker analysis. Age of patients was (57.2±13.7) years old and (53.1±14.1) years old in the FNA group and the FNB group, respectively (P=0.178). Size of lesions between the FNA group and the FNB group were similar [(3.8±2.5) cm vs (4.0±1.5) cm, P=0.629]. Additional baseline characteristics as well as stratification by FNA or FNB were demonstrated in Table 1.

Table 1.

Patients and cyst characteristics

Classification	n	Age/years	Female/[No.(%)]	CT/MRI characteristics/[No.(%)]
				Median cyst diameter >30 mm	Dilated main pancreatic duct (>5 mm)	Mural nodules	Cyst communication with pancreatic duct
EUS-FNA	52	57.2±13.7	27(51.9)	25(48.1)	19(36.5)	1(1.9)	8(15.4)
EUS-FNB	38	53.1±14.1	14(36.8)	26(68.4)	13(34.2)	3(7.9)	6(15.8)
t/Z/χ 2		1.375*	2.013†	3.701†	0.052†	1.844†	0.003†
P		0.178	0.200	0.084	1.000	0.307	1.000
Malignant lesion	40	59.2±12.8	20(50.0)	25(62.5)	16(40.0)	3(7.5)	5(12.5)
Benign lesion	50	52.5±14.3	21(42.0)	26(52.0)	16(32.0)	1(2.0)	9(18.0)
t/Z/χ 2		2.300*	0.573†	0.998†	0.621†	1.583†	0.512†
P		0.024	0.525	0.393	0.508	0.319	0.566

Classification	EUS characteristics/[No.(%)]			Experimental examinations
	Dilated main pancreatic duct (>5 mm)	Mural nodules	Cyst communication with pancreatic duct	Total cyst amylase/(U·L-1)	Pancreatic cyst amylase/ (U·L-1)	Cyst CEA/ (ng·mL-1)	Cyst CA19-9/ (U·mL-1)
EUS-FNA	20(38.5)	7(13.5)	9(17.3)	34 513.1±105 631.0	28 289.5±88 804.1	30.7±74.6	216.3(43.5, 373.2)
EUS-FNB	14(36.8)	8(21.1)	6(15.8)	18 779.0±40 502.1	13 585.4±28 653.6	50.7±122.4	201.0(28.7, 411.7)
t/Z/χ 2	0.024†	0.911†	0.0036†	0.872*	0.983*	-0.959*	-0.033‡
P	1.000	0.397	1.000	0.386	0.328	0.340	0.974
Malignant lesion	17(42.5)	10(25.0)	5(12.5)	3 466.5±12 893.0	2 596.0±8 890.4	57.9±110.8	211.0(43.5, 395.5)
Benign lesion	17(34.0)	5(10.0)	10(20.0)	47 392.4±109 341.7	37 669.2±91 126.9	24.2±83.6	197.1(28.4, 369.0)
t/Z/χ 2	0.683†	3.600†	0.900†	-2.816*	-2.705*	1.642*	-0.804‡
P	0.512	0.087	0.404	0.007	0.009	0.104	0.421

Classification	Lump size/cm	Cyst location/[No.(%)]				Final diagnosis/[No.(%)]
		Head	Neck	Body	Tail	Intraductal papillary mucinous carcinoma	Solid pseudopapilloma	Pancreatic adenocarcinoma
EUS-FNA	3.8±2.5	23(44.2)	7(13.5)	14(26.9)	8(15.4)	2(3.8)	1(1.9)	11(21.2)
EUS-FNB	4.0±1.5	18(47.4)	2(5.3)	9(23.7)	9(23.7)	3(7.9)	2(5.3)	10(26.3)
t/Z/χ 2	-0.398*	2.424†				—
P	0.692	0.491				—
Malignant lesion	4.0±1.8	12(30.0)	4(10.0)	14(35.0)	10(25.0)	5(12.5)	3(7.5)	21(52.5)
Benign lesion	3.7±2.4	29(58.0)	5(10.0)	9(18.0)	7(14.0)	—	—	—
t/Z/χ 2	0.672*	7.761†				—
P	0.503	0.051				—

Normally distributed continuous variables are expressed as mean±standard deviation and abnormally distributed continouous variables are expressed as median (first quartile, third quartile). *t value, †χ ² value, ‡Z value. PCLs: Pancreatic cystic lesions; CT: Computed tomography; MRI: Magnetic resonance imaging; CEA: Carcinoembryonic antigen; CA19-9: Carbohydrate antigen 19-9; FNA: Fine-needle aspiration; FNB: Fine-needle biopsy.

Table 1 also compared demographic, clinical, and cystic features of patients in malignant and benign groups. There was a significant difference in age between malignant and benign [(59.2±12.8) years old vs (52.5±14.3) years old, P=0.024]. In addition, cyst amylase was lower in malignant cysts than in benign cysts (P<0.05). Although the CA19-9 level was higher in malignant cysts than benign cysts, there was no significant difference [211.0(43.5-395.5) U/mL vs 197.1(28.4-369.0) U/mL, P=0.421].

2.2. Diagnostic yield

In the FNA group, 3 cases of benign PCLs were ultimately confirmed as mucinous cystic adenocarcinoma and pancreatic adenocarcinoma by surgery. In the FNB group, 2 cases of benign PCLs were confirmed as solid pseudopapillary tumor and pancreatic adenocarcinoma by surgery.

The accuracy, sensitivity, specificity, PPV, and NPV of EUS-FNA were 94.2%, 87.0%, 100.0%, 100.0%, and 90.6%, respectively, and those of EUS-FNB were 94.7%, 88.2%, 100.0%, 100.0%, and 91.3%, respectively. The diagnostic yield of FNB was slightly higher than that of FNA, but there was no significant difference (P>0.05, Table 2).

Table 2.

Diagnostic yield in FNA and FNB

Methods	n	Accuracy/%	Sensitivity/%	Specificity/%	PPV/%	NPV/%
EUS-FNA	52	94.2	87.0	100.0	100.0	90.6
EUS-FNB	38	94.7	88.2	100.0	100.0	91.3
χ 2		0.096	0.046	—	—	<0.001
P		1.000	1.000	—	—	1.000

PPV: Positive predictive value; NPV: Negative predictive value.

2.3. Specimen adequacy

The number of punctures in EUS-FNA and EUS-FNB was (1.7±1.1) and (2.0±1.4), respectively (P>0.05). The specimen acquisition ability of FNB was slightly higher than that of FNA, but the difference was not significant (P>0.05, Table 3).

Table 3.

Comparison of specimen adequacy in FNA and FNB

Methods	n	0	Cytology (1-2)		Histology (3-5)
			1	2	3	4	5	4-5
EUS-FNA	52	0	1	14	0	4	33	37
EUS-FNB	38	0	2	4	1	13	18	31
χ 2		—	—	—	—	—	—	1.173
P		—	—	—	—	—	—	0.324

Categorical variables are expressed as quantity.

2.4. Safety

In the FNA group, 3 cases (5.8%) had adverse events, of which 1 case was bleeding at the puncture site and was treated with peptide clip for hemostasis; 2 cases were infected after operation and improved after anti-infective treatment. Adverse events occurred in 2 cases (5.3%) in the FNB group, both of which were pancreatitis caused by postoperative pancreatic fluid leakage. After inhibition of pancreatic enzyme secretion and anti-infection treatment, the patients were cured. No significant difference was observed between the 2 groups (Table 4).

Table 4.

Comparison of adverse events in FNA and FNB

Methods	n	Bleeding	Infection	Pancreatitis	Total
EUS-FNA	52	1(1.9)	2(3.8)	0(0.0)	3(5.8)
EUS-FNB	38	0(0.0)	0(0.0)	2(5.3)	2(5.3)
χ 2		0.739	1.495	2.799	0.011
P		1.000	0.507	0.176	1.000

Categorical variables are expressed as No.(%).

3. Discussion

With the aging of the population and advances in radiologic technology, PCLs are being detected with increasing frequency. Accurate diagnosis is critical for the selection of treatment. EUS is the optimal method for evaluating PCLs, nevertheless, it remains difficult to determine the nature of PCLs. Benign PCLs such as SCAs can be observed and followed up, while PCLs with malignant potential like MCNs and IPMNs warrant close monitoring and even surgical intervention. A retrospective study in the United States suggested that one third of patients with PCLs accidentally detected and treated by surgery were incorrectly diagnosed before operation^[19]. Whether missed diagnosis or misdiagnosis might increase the economic and medical burden of these patients and lead to a reduced quality of life and damage to their physical and mental health.

The criteria for perform EUS-FNA for PCLs in different guidelines remains controversies, especially in terms of cyst size. Nevertheless, it is generally accepted that EUS-FNA should be performed if the diagnosis results are likely to alter management, and especially for PCLs with high risk factors such as cyst diameter >3 cm, main pancreatic duct dilatation >5 mm, existence of mural nodules or solid components^{[8, 20-21]}.

Among the patients enrolled in our study, the number of cases with extension of the main pancreatic duct (diameter >5 mm) did not show significant discrepancy between benign and malignant (42.5% vs 34.0%, P>0.05). This may be related to the fact that there are more patients with IPMNs in the benign group. And because we included more patients with pseudocysts and IPMNs, the proportion of patients with pancreatic duct communication with cysts was higher in the benign group than that in the malignant group (P<0.05). Mural nodules were more common in the malignant group than those in the benign group (25.0% vs 10.0%, P=0.08), elucidating that mural nodules may be a risk factor for malignant PCLs regardless of no significant statistical difference. In our results, the age of the malignant group was significantly higher than that of the benign group (P<0.05). This suggests that age may be a risk factor for malignant degeneration of PCLs.

EUS-FNA has a high specificity (88%-97%) in the diagnosis of malignant PCLs^[9-10]. It can identify diseases by cystic fluid, amylase, CEA, glucose level, next-generation sequencing, and other tests. In clinical practice, cyst CEA is widely used to distinguish MCNs from SCAs, in which the level ≥192 ng/mL is regarded as the cut-off yield^[22]. Recently, Park, et al^[23] found that the glucose level in the cystic fluid was extensively lower in MCNs than that in non-MCNs (5 mg/dL vs 82 mg/dL, P=0.002). In 2019, Lopes, et al^[24] discovered that the combination of low level glucose and high concentration cyst CEA could predict MCNs. Singhi, et al^[25] implemented next-generation sequencing of cystic fluid and found that KRAS/GNAS mutations were highly specific for MCNs, and a compound alteration of TP53/PIK3CA/PTEN was a marker of advanced cancerous stages. Due to the low concentration of tumor cells in the cystic fluid, the accuracy and sensitivity of EUS-FNA for cystic fluid acquisition and analysis of cytology are low, particularly in terms of unilateral or oligocystitic PCLs. It is more accurate to identify PCLs by directly acquiring cystic wall tissue for histological examination. As technology evolves, EUS-through-the-needle biopsy (EUS-TTNB) and EUS-guided fine needle-based confocal laser endomicroscopy (EUS-nCLE) have been gradually applied to PCLs^{[4, 18, 26-28]}. However, there is still no sufficient evidence to verify their role in determining or excluding the existence of malignancies before surgery.

In 2020, Phan, et al^[29] first reported that FNB was used to PCLs, and its diagnostic yield was 87.2%. In our study, the diagnostic yield of EUS-FNB for PCLs was 94.7%, which was relatively higher. Furthermore, we contrasted the diagnostic yield of EUS-FNA and EUS-FNB in PCLs for the first time. We found that FNA and FNB had comparable diagnostic yield in PCLs (94.2% vs 94.7%, P>0.05), which was consistent with the previous results of EUS-FNA/FAB in pancreatic solid lesions^[11]. The sensitivity and negative predictive yield of FNB were slightly higher than those of FNA. There were 3 cases of malignant PCLs diagnosed as benign by FNA, and 2 cases of malignant PCLs diagnosed as benign by FNB. The misdiagnosis yield was no significant difference (P>0.05).

We found that FNB possessed a superior ability to obtain sufficient specimens versus FNA for diagnosis in PCLs (81.6% vs 71.2%, P>0.05), in spite of no statistically significant difference. This may correlate with the small diameter of PCLs and the large number of patients with simple PCLs (cystic lesions without solid components) in our included patients. In solid pancreatic lesions, Elhanafi, et al^[30] found that EUS-FNB was better than EUS-FNA in obtaining sufficient tissue samples for histopathology and next-generation sequencing (90.9% vs 66.9%, P=0.02). Hitherto, no relevant studies have been conducted in PCLs.

EUS-FNA has been demonstrated to be a very safe procedure for diagnosis of PCLs in many studies^[31-32]. Since the application of EUS-FNB in PCLs, postoperative adverse events have been reported successively. The lateral pore structure of FNB allows more specimen to be obtained and also increases the chance of severing the pancreatic duct. In 2021, Luo, et al^[33] reported a case of patient with PCLs who occurred severe pancreatitis with respiratory failure after EUS-FNB. In Phan, et al’s study^[29], the incidence of adverse events was 8.5%. In our study, adverse events were minimal, at 5.8%. In a comparison of FNA and FNB, the incidence of adverse events was not statistically significant. With 1 case of mild bleeding after puncture treated with hemostatic clip placement and 2 cases of infection after puncture treated with antibiotics in the FNA. And with 2 cases of acute pancreatitis after puncture treated with pain control and fluids in the FNB. The 2 adverse events caused by FNB were acute pancreatitis on account of pancreatic fluid leakage after puncture, which were more serious than those in the FNA. This suggests that we should be alert to the risk of pancreatitis when performing EUS-FNB in patients with PCLs.

Our study has some limitations. Firstly, it is a retrospective study conducted at a single center, with a small sample size and did not separate solid components from cystic lesions. In subsequent studies, we will further differentiate between cystic and cystic-solid lesions. Secondly, the results of specimen acquisition guided by EUS may be influenced by the experience abundancy of endoscopists and pathologists. Thirdly, not all patients eventually underwent surgery, so the criterion standard for the diagnosis of PCLs is not entirely based on postoperative pathology. This is a major limitation in all PCLs. Fourth, the study excluded patients who underwent EUS-FNA with 19G and 25G puncture needles, and did not compare the discrepancy in the diagnostic yield of PCLs with different puncture needle types. Larger sample size and prospective studies are still necessitated to explore the impact of diverse punctures on the specimen adequacy, diagnostic yield, and safety of PCLs.

In conclusion, EUS-FNA and EUS-FNB show equally high diagnostic rate and specimen adequacy in PCLs with an excellent safety profile. These results suggest that both FNA and FNB are good and safe diagnostic tools for PCLs.

Funding Statement

This work was supported by the Special Project for the Construction of Innovative Provinces in Hunan Province, China (2020SK2013).Open access: This is an open access article under Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0) (https://creativecommons.org/licenses/by-nc-nd/4.0/).

Conflict of Interest

The authors declare that they have no conflicts of interest to disclose.

AUTHORS’CONTRIBUTIONS

YU Xiaoyu Study design, patient inclusion, data acquisition and interpretation, statistical analysis, and manuscript writing; YE Mingmei Data acquisition and interpretation, manuscript drafting and critical revision; NI Yawen and LIU Qianqi Statistical analysis, data acquisition and interpretation; GONG Pan, HUANG Yuanyuan Manuscript critical revision; WANG Xiaoyan and TIAN Li Study design, manuscript supervision and critical revision. The final version of the manuscript has been approved and read by all authors.

Note

http://xbyxb.csu.edu.cn/xbwk/fileup/PDF/202502227.pdf