Case Report
A 52 years old woman with a large pelvic cyst was admitted to our
hospital. There was no history of other gastrointestinal conditions,
cardiovascular conditions, infection, trauma, or family history. She had
undergone right breast cancer resection 2 years ago, and the pelvic cyst
was detected by positive emission tomography in the preoperative
examination for the breast cancer. There were no symptoms and findings
of malignancy, so she was kept under observation. However, a follow-up
CT showed an increasing tendency of cystic mass in size, and she was
referred to our hospital. Her laboratory studies were unremarkable
except for CA19-9. The level of CA19-9 was 142.4U/ml. CT of the pelvis
with contrast revealed a 4.5 cm well-defined, homogenous cystic mass in
the right para-rectal area (Fig.1). The inside has a poor contrast
effect, and there are no findings suggestive of a solid component.
Pelvic MRI with contrast demonstrated a 4.4cm retroperitoneal cystic
tumor with high signal intensity on T1-weighted images in the right
para-rectal area (Fig.2). The cyst appeared continuous with the rectal
wall.
The patient underwent robot-assisted low anterior resection without a
preoperative definitive diagnosis. Epidermoid cyst, duplication cyst,
and tailgut cyst were mentioned as differential diagnoses based on the
radiological findings. Access was gained with a 8-mm supraumbilical
metallic robot port followed by four same-size ports (Fig.3). The
abdomen was insufflated to an abdominal pressure of 10 mm Hg with CO2
gas supplied by AIR SEAL® intelligent flow system. The mesorectal
dissection from the sacral promontory was continued up to the level of
puborectalis sling and the levator ani muscles. After cystic
tumor-specific mesorectal excision was performed, the clip for the bowel
clamp was applied to the distal side of the cystic tumor for transanal
bowel irrigation. The patient-side cart was rolled out after transection
of the rectum with the cyst. The umbilical wound was then extended to
retrieve the specimen and closed. For subsequent anastomosis, the double
stapling technique was performed by using a circular stapler. The
excisions of cysts were complete with macroscopically negative margins.
There was no intraoperative event and the operative time was 356
minutes.
The surgical specimens consisted of a cystic lesion from the posterior
wall of the rectal to the right side, with no continuity with the rectal
lumen (Fig.4). Histologically, most of the cyst lumen has epithelial
shedding, granulation tissue and histiocyte clusters, and numerous
cholesterin fissures and hemosiderin deposits in the thickened fibrous
connective tissue. The remaining epithelium shows morphology similar to
anal canal epithelium, which is a mixture of goblet cells in a cubic to
columnar epithelium of about five layers, and squamous epithelium-like.
The epithelium is surrounded by developed smooth muscle tissue and
transitions to skeletal muscle tissue, which is thought to be the
levator ani muscle. It is a tissue image that distinguishes between a
duplication cyst and a tailgut cyst. Although the nerve plexus is not
clear and the epithelium is not a glandular epithelium, which is not
typical as a duplication cyst, the above diagnosis was made because the
thickening of the muscular layer is conspicuous to make it a tailgut
cyst.
The postoperative course was uneventful. The patient was discharged 27
days after surgery, and she has remained in excellent health so far for
a year and 5 months.