Keywords
colorectal hamartoma - perineal tumor - posterior hypospadias - rectal duplication
Introduction
Congenital perineal lesions are rare and can occur along with other birth defects
such as anorectal malformations (ARMs).[1] We recently treated a newborn with hypospadias, however, without an ARM, who also
had a perineal tumor based on ectopic colorectal tissue, i.e., hamartoma.
Presentation
A neonate born premature at 32 weeks with a birth weight 1,740 g was evaluated for
a soft dark pink perineal tumor arising 5 mm from a normal anus with associated normal
passage of stools. He had a proximal hypospadias with a bifid scrotum and bilateral
testes ([Fig. 1a]). Although the position of the urethral meatus could not be identified, there were
no signs of urinary obstruction. Ultrasonography showed normal kidneys and urinary
tract. Karyotype is 46 XY, levels of sex hormones were normal, and genetic panel for
ARM and differences of sex development showed no mutations.
Fig. 1 (a) Photograph of the patient in supine position. (b) Preoperative photograph of the patient in prone position.
In the first 6 months the perineal lesion gradually became larger, but part from occasional
slight bleeding he remained asymptomatic. At the age of 11 months he underwent a diagnostic
examination under anesthesia with biopsy of the lesion. The narrow urethral meatus
was found immediately adjacent to the perineal lesion ([Fig. 1b]). Cystography via an inserted suprapubic catheter showed a normal bladder, short
urethra with stenotic distal part, and connection with a tubular structure posterior
of the urethra. A contrast enema showed a normal rectum and colon without duplication
or fistula. Magnetic resonance imaging (MRI) showed a perineal tumor of 13 × 6 × 15 mm
with close approximation of the urethra, the tubular structure behind the urethra
and the rectum ([Fig. 2a]). The remaining pelvic structures such as the anus, rectum, pelvic floor muscles,
and anal sphincter were unremarkable. Histological examination of the biopsy showed
colonic tissue.
Fig. 2 (a) MRI (T2) with perineal mass with fluid-filled cavity (arrow). (b) Upper panel: macroscopic aspect with central cavity (arrow). Lower panel: hamartoma alternately lined with squamous epithelium or with colorectal
mucosa. MRI, magnetic resonance imaging.
Surgical excision was scheduled at the age of 18 months. The patient had a bowel wash-out
preoperatively. Cystoscopy was performed after meatotomy of the narrow hypospadiac
urethral opening and showed a normal bladder, bladder neck, and posterior urethra
without evidence of an enlarged utricle, corresponding to the findings of the cystography.
The tubular structure entered the bulbar urethra just below the urethral sphincter
and it was blind ending. A transurethral catheter was introduced over a guidewire
and a suprapubic catheter was inserted. Complete surgical excision of the perineal
lesion was achieved with a dorsal approach and the patient in prone position. During
the procedure, a small lesion in the perineal urethra occurred and was closed. The
sphincter complex was dissected anteriorly, but the rectal mucosa remained intact.
After excision of the lesion the sphincter complex was re-approximated.
The postoperative course was uneventful. Oral intake was resumed after 5 days of parenteral
nutrition and the patient was discharged 6 days after surgery. Pathological examination
showed a solid structure consisting of smooth muscle, partly lined with squamous epithelium
and partly with colorectal mucosa and with a central cavity of 3 mm lined with cylindrical
epithelium with focal goblet cells ([Fig. 2b]).
Examination under anesthesia 2 weeks postoperatively showed slightly delayed wound
healing. The suprapubic tube was removed after micturition without residue. Wound
healing was completed 6 weeks after surgery. After extensive consultation with the
parents and the multidisciplinary team it has been decided to postpone further surgery
for hypospadias correction until the patient is older.
Discussion
Perineal lesions are uncommon and mainly occur in patients with ARM. In a series of
more than 2,000 patients with ARM, the incidence of perineal lesions was 1.5%, mainly
lipomas, hamartomas, and hemangiomas.[1] Although several case reports have been published, a series of perineal lesions
in patients without ARM is lacking. Reports of ectopic colorectal tissue presenting
as a perineal tumor in patients without ARM are even rarer. Sun et al described a
neonate with hypospadias and an inverted rectal duplication presenting as a rapidly
growing perineal mass connected with the pelvic diaphragm.[2] Our patient, however, is more similar to the case reported by Liu et al of a gradually
enlarging perineal mass in a female infant with associated vaginal duplication. The
excised perineal tumor in this case was also considered to be a hamartoma consisting
of colorectal tissue, in which no connection to surrounding pelvic structures such
as rectum or urethra was noted.[3]
The pathogenesis of congenital colorectal hamartomas of the perineum is unknown. Liu
et al mentioned that the perineum originates from the tip of the urorectal septum
which separates the urogenital sinus from the anorectal tract. The close relation
of these structures during embryologic development may explain the association of
perineal colorectal hamartomas with developmental anomalies of the anorectal and urogenital
tracts.[3] Gangopadhyay et al described two patients, the second in particular being quite
similar to our patient, although the rather blurred photographs are difficult to review.
They also hypothesized that an abnormal shape and development of the urorectal septum
underlies this condition.[4] Perineal colorectal hamartoma should be differentiated from a bowel duplication.
Duplications by definition have a close connection to a bowel segment and share a
common blood supply.[5] The perineal tumor in our case was neither connected to the rectosigmoid nor with
its blood supply and is therefore best classified as a hamartoma.
Diagnosis of a protruding perineal lesion must include radiologic examination using
ultrasonography and MRI to delineate the extent of the lesion in relation to the surrounding
structures (for example the urethra, bladder, vagina, and/or rectum) and to detect
associated malformations within these structures. Contrast studies can be helpful
to exclude a fistula to urogenital or colorectal structures. Biopsy to determine histology
may be of additional value if diagnosis after imaging and endoscopic examination is
still unclear. Treatment of a perineal lesion after establishing the precise relationship
with the surrounding structures is surgical in nature. A careful dissection with special
attention to nearby structures like urethra and rectum and use of bipolar coagulation
is important for a successful treatment.
Conclusion
Congenital perineal masses are mainly reported in association with ARM. Reports of
perineal colorectal hamartomas without ARM are exceptional. We describe the third
case in a male infant, of a perineal colorectal hamartoma associated with posterior
hypospadias. Unlike rectal duplications, no connection to adjacent structures is found
in perineal colorectal hamartomas. Given the close relationship of the developing
perineum with the urogenital and anorectal tracts, an accurate radiological evaluation
and endoscopy of the pelvic organs prior to surgical excision is recommended.
