1. Title = Tailgut cysts: report of two cases and review of the literature.
2. Running head = Tailgut cysts.
3. Authors = Dr. Eleanor Au MBBS, Mr. Oliver Anderson MRCS, Dr. Barry
Morgan MBBS, Dr. Lida Alarcon MBBS, Mr. Mark L. George FRCS
4. Institution (for all authors) = St Thomas’ Hospital, Westminster Bridge Road,
London. SE1 7EH
5. Corresponding author = Mr. Oliver Anderson. o.anderson@doctors.org.uk
6. Disclaimers = none
7. Source of support = none
8. Presentations = none
9. Word counts: Abstract = 173, Text = 2200
10. References = 35
Author contributions
OA = co-wrote the manuscript and literature review and provided the radiology
EA = co-wrote the manuscript and literature review
BM = provided the histopathology for case 1
LA = provided the histopathology for case 2
MG = reviewed and edited the paper
This is the pre-refereed version of a published paper:
Au E, Anderson O, Morgan B, Alarcon L, George ML. Tailgut cysts: report of two
cases. Int J Colorectal Dis. 2009 Mar;24(3):345-50. Epub 2008 Oct 18. Review.
PMID: 18931850
The definitive version is available at:
http://www.springerlink.com/content/k05hgwh110872211/
Abstract
Purpose We review the literature regarding the diagnosis and management of
tailgut cysts, which are also known as retrorectal cystic hamartomas and mucus
secreting cysts.
Methods We present two cases of tailgut cyst treated by surgical excision and a
review of the literature. One retrorectal tailgut cyst and a rarer prerectal tailgut
cyst.
Results Tailgut cysts are a rare developmental abnormality thought to arise from
remnants of the embryological postanal gut that normally regresses. Usually
presenting incidentally or with pressure symptoms in middle-aged females, tailgut
cysts are often initially mistaken for other clinical entities. Magnetic Resonance
Imaging is the best imaging modality to differentiate tailgut cysts from other
retrorectal lesions and developmental cysts. Histologically, the cyst wall
demonstrates a wide variety of epithelial types and has a malignant potential.
Malignancy is difficult to rule out with imaging or biopsy and therefore surgical
excision is recommended.
Conclusions Magnetic resonance imaging is the favoured imaging modality and
surgical resection is recommended to relieve pressure symptoms and rule out
malignancy in retrorectal and prerectal cystic lesions.
MeSH Key words
Congenital, Colon, Cyst
Introduction Tailgut cysts, also known as retrorectal cystic hamartomas and
mucus secreting cysts, are rare congenital lesions that are thought to be derived
from remnants of the embryonic postanal gut, which incompletely regresses
during development.(1-3)
They are almost invariably located in the retrorectal space,(2) but have also been
reported in the perirenal space, (4-6) the perianal skin (3, 7-9)and very rarely
prerectally. (2, 10, 11) We present a retrorectal tailgut cyst and also a much rarer
prerectal tailgut cyst, which has only been reported four times before.
Case reports
Case 1
A 24 year-old female presented to the Accident and Emergency Department with
acute urinary retention requiring urethral catheterisation. She gave a 2-year
history of low backache, but had no abdominal or anal symptoms. One year
previously, she had a thyroidectomy for a follicular adenoma. Clinical
examination of the abdomen revealed a pelvic mass and digital rectal
examination revealed a smooth, large, immobile retrorectal mass displacing the
rectum to the right hand side. It was not possible to get above the mass on rectal
examination.
Initial investigation with transabdominal ultrasonography confirmed a pelvic mass.
Computed Tomography (CT) with contrast demonstrated a low attenuation lesion
in the retrorectal space. Magnetic Resonance Imaging (MRI) with contrast
confirmed a 9x11x11cm cystic mass in the retrorectal space, (Figure 1)
displacing the rectum, anal canal and distal sigmoid to the right and the vagina
anteriorly. The cyst was well defined, thin walled, unilocular and extended into
the right ischioanal fossa. The cyst was adherent to the left posterolateral wall of
the rectum, but did not invade the sacrum. On T1-weighted MRI the lesion was
low signal and on T2-weighted MRI the lesion was high signal. There were no
areas of heterogeneity or irregularity that enhanced with contrast.
The patient underwent a low anterior resection with a hand sewn coloanal
anastomosis and loop ileostomy. The retrorectal cyst was excised completely.
(Figure 2) Postoperative recovery was complicated by a left ischioanal fossa
collection secondary to a contained leak from the coloanal anastomosis. This
required two CT-guided percutaneous drainages. The patient then made a good
recovery. A gastrograffin enema, at three months postoperatively, showed no
leak from the coloanal anastomosis and the patient had uncomplicated ileostomy
closure.
On histopathological examination, the macroscopic specimen consisted of a
unilocular 11x6.5x4cm collapsed cyst attached to the posterior mesorectal
surface by a 3x2cm stalk of connective tissue. The inner aspect of the cyst had
an irregular, yellow surface with some mucoid fluid content. (Figure 2)
Microscopically, the cyst was partially lined by non-keratinising squamous
epithelium. (Figure 3) In other areas, it was lined by granulation tissue with
numerous foamy macrophages, scattered foreign body type multinucleated giant
cells and cholesterol crystals. The underlying stroma showed chronic
inflammation and fibrosis.
Case 2
A 60 year-old gentleman, with a past medical history of idiopathic epilepsy, had
an abdominal ultrasound scan for the investigation of very mildly deranged liver
function tests. The ultrasound scan coincidentally detected a pelvic cystic mass
and left-sided hydronephrosis. Abdominal and digital rectal examinations were
unremarkable. A subsequent CT scan with contrast revealed a partially calcified,
lobulated cystic mass situated posterior to the bladder and anterior to the rectum.
The cyst displaced the bladder to the right and was extrinsically compressing the
distal left ureter causing left hydronephrosis. (Figure 4) The differential diagnosis
based on the CT scan included a large bladder diverticulum with tumour within it
or a tumour of the seminal vesicles or prostate. However, a transrectal
ultrasound scan showed the lesion was not arising from the seminal vesicles or
prostate and cystoscopy demonstrated that the bladder was normal.
Percutaneous needle biopsy of the cyst was inconclusive, showing only
mucinous and inflammatory material with no malignant cytology.
The patient was managed with the insertion of a JJ stent at cystoscopy to relieve
the left-sided hydronephrosis. Laparotomy revealed an anterior-rectal cystic
lesion, adherent to both ureters and to the small bowel and rectum. Frozen
section of the cyst wall was inconclusive showing only infammaory cells. An
anterior resection and defunctioning ileostomy was performed and the patient
made an uneventful recovery.
On histopathological examination, the macroscopic specimen consisted of a
unilocular collapsed cyst attached to the posterior mesorectal surface. The inner
aspect of the cyst had an irregular, yellow surface with mucoid fluid content.
Microscopic examination of the cyst wall showed mucinous columnar epithelium
with denuded areas lined with foamy macrophages and scattered regions of
fibrotic connective tissue associated with multinucleated foreign body giant cells
with cholesterol clefts. There was no bowel mucosa, organized smooth muscle
layers or neural plexus. (Figure 5)
Discussion
Tailgut cysts are believed to arise from the remnants of the embryonic hindgut.
During the 3.5 mm to 8 mm gestational stage (28-35 days) of human
development, the embryo possesses a true tail, which is caudal to the site of the
subsequent formation of the anus. The primitive hindgut extends into this tail,
which usually completely regresses by the 8th week of gestation. (12) The
persistence of this postanal gut in the retrorectal space is hypothesized to be the
origin of the tailgut cyst. (1, 2)
Tailgut cysts predominantly present in middle-aged women with an average age
of 35 and a male to female ratio of approximately 1:3. (2, 13, 14)
Tailgut cyst has been described in infants, strengthening the theory that it is a
congenital condition. (3)
Symptoms of mass effect or pain are present in 50% and include rectal fullness,
bleeding and pain on defaecation, constipation, lower abdominal and back pain
and symptoms associated with genitourinary obstruction.(2, 13, 15)
A large proportion of cases are initially misdiagnosed. The patient may present
with a history of multiple drainage procedures for recurrent pilonidal abscess,
perianal abscess or fistula in ano. (2)
On digital rectal examination, a mass is usually palpable in the retrorectal
space.(2) However, few cases have been reported showing that tailgut cysts can
occupy other positions in the perirenal space (4-6) the perianal skin (3, 7-9) and
prerectally. (2, 10, 11)
Cases of malignancies that have been reported to be associated with a tailgut
cyst include adenocarcinomas, carcinoid tumours, neuroendocrine carcinomas,
endometrioid carcinoma, adenosquamous carcinoma, squamous cell carcinoma
and sarcoma. The majority are adenocarcinomas, and carcinoid tumours. (2, 9,
13, 14, 16-23)
Adenocarcinomas arising from tailgut cysts may have p53 gene mutations similar
to colorectal adenocarcinoma. These cysts also demonstrated dysplasia,
suggesting a dysplasia-carcinoma sequence. (18)
Adenocarcinoma arising in a tailgut cyst has occasionally been shown to be
positive for CEA and serum CEA and CA19.9. Tumour markers that have been
shown to indicate tailgut cyst tumour recurrence.(17, 19, 20, 24)
Radiological Features
Localisation of the cyst in the retrorectal space may be difficult with
transabdominal ultrasound and can be mistaken for an adnexal mass,(25)
however it may reveal whether the cyst is uni or multilocular.
Transrectal ultrasound may be useful in demonstrating the integrity of the layers
of the rectum, showing absence of invasion in a benign lesion.(26)
Cross-sectional imaging techniques are more reliable at defining the location of
the cyst in the retrorectal space. (25)
When the location of a retrorectal cyst is known there is still a large radiological
differential diagnosis; epidermoid cyst, dermoid cyst, rectal duplication,
neuroenteric cysts, cystic sacrococcygeal teratoma, anterior sacral meningocele,
necrotic rectal leiomyosarcoma, extraperitoneal adenomucinosis, cystic
lyphangioma, pyogenic abscess, neurogenic cyst, necrotic sacral chordoma and
tailgut cyst. (14)
A prerectal cyst differential diagnosis includes; utricle cyst of the prostate, simple
cyst of the prostate, rectal duplication, simple cyst of the seminal vesicle and
bladder diverticulum. (11, 27, 28)
CT usually demonstrates a thin-walled, well-circumscribed retrorectal mass with
septations. When the mass is large, the rectum may be displaced. The low
attenuation of the contents varies according to the consistency of mucin and
inflammatory debris.(25, 29)
Calcifications may be seen in the cyst wall although they are more commonly a
feature seen in dermoid cysts, teratoma and other retrorectal space lesions (e.g.
neuroblastoma, chordoma and mucinous adenocarcinoma).(23, 25, 30)
Infection may cause a wall thickening along with other signs of local inflammation.
Invasion of adjacent structures and loss of discrete margins are important signs
of malignancy. (25, 29)
Tailgut cysts usually have a low signal intensity on T1-weighted images and high
signal intensity on T2-weighted images.(31, 32)
MRI is more sensitive than CT at differentiating unilocular and multilocular
masses, and especially for the detection of small peripheral cysts.(32) The cyst
wall and septa usually enhance with gadolinium, as do areas of malignant
transformation and infection. Malignancy is suspected if there is a heterogeneous
thickening with an irregular margin, invasion into the pelvic sidewall or adjacent
pelvic viscera and intermediate signal before contrast on both T1 and T2weighted images with enhancement after contrast.(19, 22, 30, 31) Recurrent
benign tumours may be heterogenous and have irregular margins and be
indistinguishable from malignancy.(33)
Histopathological Features
The histopathological features that help differentiate tailgut cysts from the other
types of developmental cysts are the cell types in the lining of the cyst.
Gross examination of a tailgut cyst usually reveals a multilocular cyst ranging in
size from 1 cm to 15 cm with a clear, thick mucoid fluid content. The cyst wall can
be lined by a variety of epithelia; stratified squamous, columnar, cuboidal, ciliated
columnar, mucinous, gastric and transitional. Scattered bundles of smooth
muscle fibres are usually present in the cyst wall separated from the epithelium
by a thin layer of fibrous tissue. (2, 13, 14)
Epidermoid cysts are unilocular and lined with stratified squamous epithelium
and contain clear fluid. Dermoid cysts are similar to epidermoid cysts, but also
contain skin appendages (e.g. hair follicles, sweat glands). Rectal duplication is
defined by 3 histological criteria; continuity with the rectum, a smooth muscle
coat with myenteric plexus, and a mucosal lining reflective of the gastrointestinal
tract with muscularis mucosae, villi and crypts. Teratomas contain derivatives
from all 3 embryonic germ cell layers: ectoderm (squamous epithelium, and skin
appendages), endoderm (respiratory or gastrointestinal epithelium, and
pancreas), and mesoderm (connective tissue, smooth muscle, cartilage and
bone). Neurenteric cysts differ from tailgut cyst in that they contain a well defined
lamina propria and a more mature mucosa of endodermal origin (e.g. intestinal,
bladder).(2, 13, 14, 30)
It has been suggested that tailgut cysts may be classified as teratomas, because
they contain evidence of ectoderm (squamous epithelium), endoderm
(respiratory ciliated epithelium) and mesoderm (smooth muscle).(13, 24)
However, the ciliated columnar epithelium may have persisted from the
embryological gastrointestinal tract and squamous epithelium may be due to
metaplasia. (2)The term teratoma is reserved for cysts demonstrating dermal
appendages, neural elements, cartilage or bone. (14)
The differential diagnosis of prerectal tailgut cyst includes; rectal duplication,
utricle cyst of the prostate, which is lined by columnar or cuboidal epithelium and
continuous with the utricular wall,(34) and simple cyst of the seminal vesicle,
which is lined by cuboidal or squamous epithelium with a fibrous wall and sperm
within. (11)
Management
All retrorectal cysts should be assessed for malignancy with radiological imaging
and biopsy for histology.
Unfortunately, definitive diagnosis and particularly differentiation of tailgut cysts
from the other developmental cysts is usually not possible on diagnostic biopsies,
including needle biopsy and frozen sections, as was the case in the second of
our patients. Although diagnosis has been reported with ultrasound-guided
needle biopsy,(35) a diagnostic biopsy is generally not advised because it may
miss foci of malignancy. Even if the biopsy does sample a malignancy, it carries
the risk of spillage and seeding of tumour cells. (14)
If there is a low index of suspicion for malignancy and patients are asymptomatic,
routine surveillance may be appropriate. However, surgical resection provides a
specimen that is sufficient for histopathological examination to give a definitive
diagnosis, relieves symptoms caused by mass effect, avoids subsequent
infection and rules out malignant transformation.
Conclusion
Tailgut cysts are a rare developmental disorder either presenting with pelvic
pressure symptoms or are incidental findings on scanning. They are usually
palpable rectally. The preoperative diagnosis depends primarily on correct
localization of the cyst, which is usually in the retrorectal space, this is most
accurately provided by MRI. The recommended treatment is complete surgical
excision to provide a definitive diagnosis, relieve pressure symptoms and
exclude malignant transformation.
Acknowledgements
None
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Figure 1
Sagittal plane T2-weighted MRI showing the high-signal retrorectal cyst
Black arrow = cyst, white arrow = rectum
Figure 2
Opened cyst and specimen of colon showing the pedicle of the cyst and the inner
lining of the cyst
Figure 3
Cyst wall partially lined by non-keratising stratified squamous epithelium
Figure 4
Axial plane CT showing the low attenuation tail-gut cyst in front of the rectum
Black arrow = cyst, dashed arrow = bladder, white arrow = rectum
Figure 5
Cyst lining containing foamy macrophages, multi-nucleated giant cells and
cholesterol clefts.