Patients with classical familial adenomatous polyposis (FAP) present with hundreds
of colorectal adenomas requiring (sub)total colectomy at around age 20 years, and
frequently duodenal adenomas. Duodenal polyposis is a progressive disease. The burden
of duodenal adenomas evolves more slowly as compared to colorectal adenomas, but increases
with age to the highest stage of duodenal polyposis, stage IV according to the Spigelman’s
classification, with an expected cumulative frequency of 50 % at age 70 years [1]. Although the surveillance recommendations are relatively clear and homogeneous
in the different countries, with the first duodenal surveillance between 20 and 25
years, the modalities of treatment are much less well defined.
Duodenal adenomas either ampullary or peri-ampullary present usually as flat, whitish,
small lesions and slightly elevated as compared to the surrounding mucosa. There is
a majority of small (< 5 mm) lesions, and some larger lesions depending on the severity
of the duodenal polyposis. Endoscopists have to focus on the detection and characterization
of larger (> 1 cm) lesions as these have been shown to contain foci of high-grade
dysplasia in up to 50 % of cases and have been associated with a risk of cancer development.[2]
[3] The role of the endoscopist during duodenal surveillance is to 1) detect any existing
cancer (complete evaluation of the duodenum and firsts jejunal loops); and 2i) evaluate
the burden of duodenal adenomas in order to estimate the risk of advanced neoplastic
evolution and the adapted surveillance interval. The only available criterion nowadays
is the Spigelman’s classification, which includes the number (< 10, 10 – 20, > 20),
the size (< 5 mm, 5 – 10 mm, > 10 mm) and the histology (low- or high-grade dysplasia)
of duodenal adenomas. Optimal endoscopic examination of the duodenum, with lateral
viewing and axial viewing at the same time, using a long endoscope to visualize the
proximal jejunum and indigo-carmine to improve visualization of the mucosa, although
relatively consensual for expert centers, has not really been validated through prospective
studies. At least, indigo-carmine dye has been shown to increase the number of adenomas
detected in two series and to increase the Spigelman’s score.[4]
[5]
The question addressed in the paper by Pittayanon and colleagues [6] is that of the diagnostic value of new imaging methods (narrow band imaging and
confocal microscopy) as regards the identification of duodenal adenomas. The main
clinical question in this disease should be: What are the limitations of present surveillance
modalities, what is the reference method of examination, and do we need new methods
to improve surveillance? The main limitation of the usual surveillance of duodenal
polyposis would be to overlook major neoplastic area that would evolve into cancer
during the recommended surveillance interval (2 – 3 years). Some old retrospective
series suggest such a limitation, but these are mainly based on a largely obsolete
methodology (axial viewing, old endoscopes, no sedation) [3]. In contrast, recent prospective series, even in patients with severe duodenal polyposis,
do not suggest a high frequency of overlooked precancerous lesions [7]. Finally, the recent progress of usual endoscopes into high-definition endoscopy
will probably replace, based on our experience, even indigo-carmine dye, given the
excellent visualization of even tiny adenomas. And this evolution is still underway,
given the new generation of endoscopes that are under development or research. Thus,
there will probably be no clinical need for new technologies to identify more duodenal
adenomas in FAP patients.
On the other hand, is it important to differentiate duodenal adenomas from other duodenal
polyps, as proposed by Pittayanon and colleagues? There is a real concern regarding
the duodenal bulb as some lesions can mimic duodenal adenomas in this area, including
gastric metaplasia and Brunner glands. There is also a question regarding the identification
of adenomatous tissue on the duodenal papilla, especially because biopsies, although
with a very low frequency, can induce pancreatitis. In the latter case, however, it
would be important to determine whether microscopic (macroscopically invisible) ampullary
adenoma represent a danger for patients even on a long-term basis, given the very
slow evolution of duodenal adenomas [8]. In our experience, we usually leave in place small, flat, visible ampullary adenomas
for years. Regarding the numerous small duodenal adenomas observed throughout the
proximal and distal duodenum of patients with FAP, there is no recommendation to biopsy
and thus confirm the diagnosis of adenomas, as there is almost no differential diagnosis
in this area. Practically, we never take numerous biopsies of these lesions, but simply
count the number of adenomas to get a satisfying evaluation of the Spigelman’s score.
For these reasons, identifying exactly the nature of small whitish lesions in the
proximal and distal duodenum is probably of low clinical relevance. Moreover, if this
was of any clinical relevance, any new diagnostic method should be compared with simple,
white-light imaging, and probably to the reference method, i.e indigo carmine dye.
Finally, what is important for patients with FAP regarding duodenal examination? Three
measures: 1) beginning relatively early surveillance, around age 20 years, as we observe
severe polyposis in a low number of young patients; 2) following recommended modalities
of examination, including anesthesia, lateral and axial viewing, examination of the
proximal jejunum to identify all possible areas of advanced neoplasia; and 3) being
very cautious with large (> 1 cm) adenomas, which should be removed because they represent
a significant risk of high-grade dysplasia or cancer. We should keep in mind that
this evaluation needs to be done at regular intervals, is time consuming, and should
remain relatively simple so that gastroenterologists can keep on doing an excellent
and regular evaluation of this significant risk of duodeno-jejunal cancer in patients
with FAP.
