10.1055/a-0967-4684The limitations of transabdominal ultrasound in diagnosis of pancreatic diseases [1] were the driving force in developing endosonography (EUS) with the first echoendoscope
being launched in 1980 [2]. The curvilinear array design of modern echoendoscope transducer heads enables EUS-guided
sampling of lesions [3]. Traditionally, the principal sampling technique has been EUS-guided fine-needle
aspiration (EUS-FNA) with open-tip needles designed for cytology [4].
Among all neoplasms originating from the pancreas, pancreatic neuroendocrine tumors
(PanNETs) constitute a relatively rare entity. Incidence of PanNETs reportedly is
increasing [5], and these tumors are challenging to diagnose with imaging alone [6], which implicates sampling of lesions suspected for PanNET. In addition, immunostaining
for entity-specific tumor markers is required for reliable microscopic diagnosis [7].
Problematically, EUS-FNA is suboptimal in solid pancreatic lesions, with an 85 % sensitivity
for malignancy [8]. Furthermore, a majority of publications include mostly or exclusively pancreatic
ductal adenocarcinomas [9]
[10]. The few studies addressing PanNETs have shown varying diagnostic sensitivity for
EUS-FNA, ranging from 47 % [11] to 90 % [12], ([Fig. 1]).
Fig. 1 EUS-FNA of a hypoechoic, highly vascularized PanNET.
In recent years, a new generation of biopsy needles (EUS-FNB [fine-needle biopsy])
has been developed for acquisition of whole tissue samples [13]
[14]
[15]. At present, it is not known whether FNB needles and processing of histology specimens
can improve diagnosis of suspected PanNETs and motivate a shift from EUS-FNA.
In this issue of Endoscopy International Open, Eusebi et al contribute new knowledge
on this important topic by investigating the diagnostic yield and sensitivity of EUS-FNB.
The study has a retrospective design and it was conducted in a two-center setting
during a 13-year period (2004−2017). Exclusively PanNETs were included and 102 EUS-guided
sampling procedures were analyzed in 91 patients. Sampling was performed either by
EUS-FNA (22/25-gauge needle), by EUS-FNB, or by both modalities. From 2004 to 2011,
a 19-gauge Quick-Core FNB-needle (Cook Medical, Limerick, Ireland) was used while
using a 22/25-gauge reverse bevel ProCore FNB-needle (Cook Medical) or a 22-gauge
opposing bevel SharkCore FNB-needle (Medtronic, Minneapolis, Minnesota, United States)
from 2011 to 2017.
The authors report that the diagnostic yield, i. e. the acquisition of a macroscopically
adequate sample, was 85 % (35/41) in EUS-FNB and 78 % (69/89) in EUS-FNA. In an intention-to-diagnose
analysis, the final diagnostic sensitivity of EUS-FNB and EUS-FNA was 80 % (33/41)
and 69 % (61/89), respectively. In dual sampling procedures (n = 28), the combination
of EUS-FNB and EUS-FNA had a significantly higher diagnostic yield than EUS-FNA alone,
96 % (27/28) vs 75 % (21/28), P = 0.023. Either of the two techniques was diagnostic for PanNET in all of the 27
adequate samples. Seven EUS-FNA samples were inadequate for a conclusive diagnosis
and in six of seven of these cases (86 %), the EUS-FNB sample was diagnostic. On the
other hand, in six cases EUS-FNB was non-diagnostic and in all of these six cases,
EUS-FNA was diagnostic. No noticeable difference in diagnostic performance was seen
between the three FNB needles. No adverse events were recorded after EUS-FNB, which
is a finding in line with the results of other studies [14]
[16].
The study by Eusebi et al is important because a high number of patients were included
and small PanNETs were not excluded. Moreover, few studies on EUS-FNB have been performed
in cohorts containing exclusively PanNETs [17]. There are some weaknesses in the study discussed by the authors. As an example,
different types of FNB needles were used, one of which – the Quick-Core needle – has
been discarded by most endosonographers due to a high frequency of technical failures
and a low diagnostic accuracy [18].
According to a recent study on solid pancreatic lesions [19], the accuracy of the reverse bevel FNB needle was found inferior (74 %) to that
of the opposing bevel FNB needle (92 %). The number of cases sampled by EUS-FNB in
the study by Eusebi and co-workers was not sufficient to determine which FNB needle
is the superior one. Furthermore, there are yet other FNB needles available, such
as the Franseen tip needle [20].
Importantly, the comparison of EUS-FNB and EUS-FNA is not exclusively a comparison
between needles but rather a comparison between two different diagnostic approaches,
which also include sampling maneuvers, sample preparation, and sample assessment by
the (cyto)pathologist. Poor quality at any of these steps will result in a non-diagnostic
work-up. This is a crucial aspect to keep in mind when interpreting studies investigating
the accuracy of EUS-guided sampling.
Even though Eusebi and co-workers present valuable new data, it remains to be decided
to what extent EUS-FNB may be superior to EUS-FNA in the work-up of suspected PanNETs.
This study, like others [21], shows that EUS-FNB is a useful adjunct to EUS-FNA. Whether EUS-FNB should be used
as the primary technique, or as a rescue technique after an unsuccessful EUS-FNA,
warrants further investigation. Studies analyzing the benefit of combining a 25-gauge
FNA needle and a 22-gauge reverse bevel FNB needle in the same solid pancreatic lesion
have shown contradictory results [21]
[22]. Moreover, such an approach implicates increased costs and a prolonged procedural
time. Therefore, dual-modality sampling should be considered only in strictly selected
cases. Future studies focusing on PanNETs should be designed as prospective, randomized
trials using a predefined set of FNA and FNB needles with surgical specimens as the
reference standard.
