Keywords appendix - carcinoid - pediatric - antegrade continence enema
Introduction
Since it was first described in the early 1980s, first by Mitrofanoff and then by
Malone (antegrade continence enema [ACE]) the appendix has been used as a catheterizable
conduit, for both bladder and bowel.[1 ]
[2 ] Although use of ileum, ureter, and even fallopian tube has also been described,
the appendix remains the most commonly used conduit.
We describe a case of incidental carcinoid tumor in the tip of an appendix used for
an ACE procedure.
Case Report
A 9-year-old boy, with previous anorectal malformation, corrected with a posterior
sagittal anorectoplasty (PSARP), developed neuropathic bladder and bowel. He underwent
an ileocystoplasty and Monti–Mitrofanoff and appendix ACE procedure. The tip of the
macroscopically normal appendix was sent for routine histopathology, which is a standard
practice for the operating surgeon.
Microscopy demonstrated a 5-mm well-differentiated neuroendocrine tumor in the tip
of the appendix ([Fig. 1 ]), which extended into muscularis propria. Ki -67 tumor proliferation index was <2%. On hematoxylin and eosin (H&E) staining, nests
of neuroendocrine cells could be seen infiltrating into the appendix wall and involved
the proximal resection margin, and findings were confirmed on synaptophysin staining
([Fig. 2 ]).
Fig. 1 H&E stain demonstrating a mass at the tip of the appendix. H&E, hematoxylin and eosin.
Fig. 2 H&E stain demonstrating infiltrating neuroendocrine cells and nests confirmed by
positive synaptophysin staining (inset). H&E, hematoxylin and eosin.
Due to proximal margin involvement and following neuroendocrine tumor multidisciplinary
team (MDT) recommendation, the appendix conduit and surrounding skin was re-excised
and a tube cecostomy was created through a separate incision. Microscopy of the remainder
of the appendix revealed no residual neuroendocrine tumor, and no further treatment
was required. The patient remained well at the last follow-up.
Discussion
Neuroendocrine or carcinoid tumors, first described in 1867 by a Swiss pathologist
Theodore Langhans, are most frequently found in the gastrointestinal tract with two-thirds
located in the appendix.[3 ] In children, carcinoid most commonly presents with symptoms suggestive of appendicitis
or is detected when the appendix, or portion of appendix, is removed incidentally
during surgery, as was the case for our patient.[3 ]
The incidence of appendix carcinoid in children is variable, reported in between 0.08
and 0.7% of appendicectomies.[3 ]
[4 ] Even in symptomatic cases, carcinoid tumors are rarely identified at the time of
surgery. A recent systematic review of pediatric carcinoid tumors found that in 91%
cases, carcinoid was only identified following histology, as we report in our case.[5 ] The majority of studies in this review report cases of appendectomies undertaken
for symptomatology, acute appendicitis or chronic abdominal pain with a carcinoid
incidence of 0.3% of appendectomies.[5 ] Incidental appendectomies, performed in an adult population of patients with normal
appendices, demonstrated a much higher carcinoid incidence of 1.6%.[6 ]
To our knowledge, this is only the second reported pediatric case in the literature
of incidental carcinoid in an appendix conduit. The first case, reported in the late
1990s, was in a 7-year old girl who had an appendix Mitrofanoff.[7 ] Similar to our case, the appendix appeared macroscopically normal at operation and,
with the exception of excision of the residual appendix and revision of the Mitrofanoff,
the patient also required no further treatment.
While the literature reports a variety of techniques for Mitrofanoff and ACE formation,
none mentions whether the appendix conduit tip should be sent for histopathology.
However, the majority of United Kingdom surgeons we surveyed do not request routine
histology on the appendix tip when using it to form a catheterizable conduit.
Conclusion
Appendix carcinoid is most commonly diagnosed at histology and may be detected without
prior symptomatology. Appreciating this, and with the recognized, albeit small, risk
of carcinoid in the appendix conduit, we therefore recommend routine histological
examination of the appendix tip.
