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Rectal Polyps andOther Neoplasms
KelliM.BullardDunn
25
Introduction
Although adenomas, adenocarcinoma and epidermoid carcinoma compose the majority of anorectal tumors, there are a variety of other more
rare lesions that occur in the anorectum. In many
cases, diagnosis may be challenging, especially
because many patients and their caregivers attribute anorectal symptoms to hemorrhoidal disease. In this chapter, we will review the diagnosis
and treatment of both the common and the more
unusual neoplasms.
Benign
A polyp is a growth protruding from a mucous
membrane. Rectal polyps have the same morphologic and histologic characteristics as polyps
found in other parts of the large intestine and are
classied as neoplastic or nonneoplastic polyps.
The benign neoplastic polyps (also referred to as
adenomatous polyps) include tubular adenomas,
villous adenomas, tubulovillous adenomas, and
serrated adenomas. Morphologically they are
described as sessile (at) or pedunculated (on a
stalk). The varieties of nonneoplastic polyps are
K. M. BullardDunn (*)
Surgery, University of Louisville,
Louisville, KY, USA
e-mail: kbdunn01@louisville.edu
hyperplastic polyps, juvenile polyps, hamartomatous polyps, and inammatory polyps.
Adenomatous Polyps
Adenomas are the most common benign neoplasm of the gastrointestinal tract (l); 8% of all
colorectal adenomas are located in the rectum
[1]. By denition all adenomas contain dysplastic epithelium. The nuclei of adenomas are hyperchromatic, elongated, crowded and arranged in a
pseudo-stratied manner, which produces a
'picket fence' appearance. The microscopic architecture of adenomas divides them into three types
(Fig. 25.1). Tubular adenomas have elongated
crypts with adenomatous epithelium and
crowded, branching tubules are separated by normal lamina propria (Fig.25.2). Villous adenomas
have nger-like projections of normal lamina
propria, which are covered with adenomatous
epithelium (Fig. 25.3). Tubulovillous adenomas
(also called villoglandular adenoma or polyp,
mixed polyp or polypoid-villous adenoma) contain more than 25% tubular and villous components [2–4]. Serrated polyps were long thought to
be benign hyperplastic polyps with adenomatous
features. However, these lesions are now recognized to have malignant potential [5].
© Springer International Publishing AG, part of Springer Nature 2019
D. E. Beck et al. (eds.), Fundamentals of Anorectal Surgery,
https://doi.org/10.1007/978-3-319-65966-4_25
465
466
K. M. BullardDunn
a
Fig. 25.2 Histology of tubular adenoma
b
Fig. 25.1 Microscopic structure of adenomas. (a)
Tubular adenoma (pedunculated) and (b) villous adenoma
(Sessile)
Treatment
Rectal polyps can be associated with diarrhea,
hemorrhage, prolapse, and a risk of carcinoma.
However, asymptomatic rectal polyps should be
removed due to the risk of malignancy.
Risk ofMalignancy
Factors which are associated with an increased
chance of malignancy in a polyp are size, severity
of dysplasia and histologic architecture. The
Fig. 25.3. Histology of villous adenoma
majority of adenomas are less than 1cm in diameter and have about a 1% malignancy rate [1, 6].
However, approximately 10% of polyps 1–2cm
in diameter contain a malignancy and greater
than 35% of polyps over 2cm will be malignant
[1, 7]. The average size of a benign adenoma is
1 cm while those polyps with invasive cancer
average 2cm in diameter [8, 9].
Variance in polyp histologic architecture alters
the risk of malignancy, and the likelihood of a
polyp containing villous changes is directly
related to its size [1]. The majority of villous
tumors are greater than 1 cm in diameter.
Table25.1 shows the incidence of malignancy in
polyps based on size and histologic type.
Natural History
Long-term patient surveillance, historical radiologic reviews and pathologic assessments established the natural history of neoplastic colorectal
polyps. One study from the Mayo Clinic,
25 Rectal Polyps and Other Neoplasms
467
Table 25.1 Incidence of carcinoma in polyps by histologic type and size [1]
Tubular
adenoma
Tubovilous
adenoma
Villous
adenoma
Under
10mm (%)
1 10 35
4 7 46
10 10 53
10–20mm
(%)
Over
20mm (%)
Rochester, MN prior to the widespread use of
colonoscopy, reported radiologic follow-up for
226 patients with polyps greater than 1 cm in
diameter that were untreated [10]. Actuarial analysis showed a cumulative risk of cancer developing at the site of the polyp 2.5% at 5 years, 8% at
10 years, and 24% at 20years.
Muto and colleagues [6] reviewed the time
interval between identication of a neoplastic
polyp and the development of malignancy. They
reported on four patients with adenomatous polyps of the rectum who received no treatment.
Three patients developed a cancer between 5 and
13years from the time of diagnosis of their polyps. The fourth patient had a benign polyp
resected after 11years. Muto and colleagues concluded that the adenoma carcinoma sequence
was at least 5 years and could take longer.
Additionally, 10 patients with villous adenomas
were observed for 5–30years. Eight were treated
by local excision or fulguration; two patients
developed malignancies after 10 and 28years of
observation. These cases also demonstrate that a
benign tumor can be present for many years without malignant change. Additional evidence for a
time interval of at least 5years in the adenoma
carcinoma sequence is the difference in mean age
at diagnosis for adenomas (58.1 years) versus
that for carcinomas (62.1years).
Malignant Polyps
Invasive carcinoma is dened as dysplastic cells,
which penetrate through the muscularis mucosae.
Two to nine percent of endoscopically removed
colorectal polyps have malignant characteristics
and treatment is based on the histopathology of
the lesion [11]. Most current authors consider
polypectomy adequate treatment for malignant
Table 25.2 Criteria for surgery for malignant polyps
• Inadequate endoscopic margin of resection is dened
as >2mm of non-malignant colonic tissue from the
carcinoma to the cauterized margin as a clear margin
• Lymphovascular invasion
• Poorly differentiated
polyps meeting certain criteria and suggest colectomy in patients whose polyps have histopathologic characteristics which put them at high risk
for residual tumor in the bowel wall, lymph node
metastasis, or distant metastasis [12, 13]. Widely
accepted indications for surgical resection following polypectomy are listed in Table25.2.
Another proposed indicator for surgical resection following polypectomy is level of invasion of
the carcinoma. To facilitate optimal post-polypectomy intervention, Haggitt and Colleagues [14]
described a classication system for levels of
invasion (Figs.25.4 and 25.5). For pedunculated
polyps, Level 0 is carcinoma in situ (severe dysplasia), Level 1 is invasion through the muscularis
mucosa in the head of the polyp, Level 2 is invasion into the neck, Level 3 is invasion into the
stalk, and Level 4 is invasion into the submucosa
of the bowel wall. Sessile polyps are classied as
Level 4 if carcinoma extends through the muscularis mucosa. Haggit and colleagues [14] found
that Level 4 invasion correlated with both a higher
rate of residual cancer and nodal involvement.
Subsequently, Nivatvongs and colleagues [15]
reviewed 151 cases of patients who underwent
resection of malignant colorectal polyps and
found lymph node involvement only in patients
with Level 4 invasion.
Polypectomy technique and specimen preparation are important in establishing proper criteria to prevent unnecessary surgery. Although
complete excision is commonly accomplished
with pedunculated polyps, the piecemeal techniques used frequently with sessile lesions prevent the pathologist from determining level of
invasion and involvement of resection margins.
Histopathologic sections should include a sagittal
cut through the polyp head, neck, stalk, and
resection margin (Fig. 25.6) [16]. Histologic
preparation using this orientation allows the
pathologist and surgeon to establish the above
468
Adenocarcinoma
Sessile AdenomaPedunculated Adenoma
Le
Le
Le
Le
Le
K. M. BullardDunn
ab
Fig. 25.4 Snare polypectomy of (a) pedunculated polyp and (b) sessile polyp
Fig. 25.5 Classication
of polyps with invasive
carcinoma
vel 0
vel 1
vel 2
vel 3
vel 4
Subserosal Connective Tissue
Submucosa
described resection criteria. Using current selection criteria, residual cancer (bowel wall, regional
or distant metastasis) is found in 8–29% of
patients who undergo polypectomy for malignant
colorectal polyps [13]. Using the criteria in
Table23.2, Whitlow and colleagues [17] reported
Adenomatous Epithelium
Normal
Colonic
Mucosa
Muscularis
Mucosae
Muscularis
Propria
Adenocarcinoma
Submucosa
SubserosaI Connective Tissue
no difference in 5-year survival for patients
treated by endoscopic polypectomy or surgical
resection. The authors recommended colectomy
for patients with ‘high-risk’ polyps. Other factors
that should be considered are patient age, general
medical condition, and tumor location. Lesions
25 Rectal Polyps and Other Neoplasms
Fig. 25.6 Polyp
preparation
469
Fig. 25.7 Laparoscopic sleeve polypectomy. Courtesy of
Scott R. Steele, MD
of the rectum present the potential complication
of functional problems after proctectomy and low
anterior resection or coloanal anastomosis or the
need for abdominoperineal resection. Transanal
excision may be appropriate management in
some instances. Transanal excision is discussed
further in Chap. 22. (Figs.25.7 and 25.8)
Large Rectal Villous Tumors
Between 40 and 66% of villous tumors are found
in the rectum (Fig.25.9) [18]. They are typically
less than 6cm in diameter and located in the mid
Fig. 25.8 Laparoscopic sleeve polypectomy.
Courtesy of Scott R. Steele, MD
or distal rectum. Clinical evaluation is approximately 91 % accurate in detecting malignancy in
rectal villous tumors [18, 19]. Features which
indicate the presence of malignancy include
induration on palpation and ulceration on endoscopy. Random biopsy has proven to be less accurate than palpation [18, 20]. As with other polyps,
the nding of a villous tumor in the rectum mandates complete colonic evaluation due to the high
incidence of synchronous neoplasms. In the
absence of malignancy, large rectal villous
470
Fig. 25.9 Endoscopic
snare of rectal villous
tumor with a Frankfelt
snare. Adapted from [17]
tumors should be removed by a
sphincter-preserving technique. Transanal techniques include fulguration, snare excision, simple transanal excision, sleeve resection, transanal
endoscopic microsurgery (TEMS) and transanal
minimally invasive surgery (TAMIS).
Although fulguration treats the primary tumor
it has the disadvantage of not providing a pathologic specimen to exclude any focus of invasive
cancer. Laser ablation or photodynamic therapy
are other means of ablating the lesion which suffer from the same drawback due to absence of a
specimen. Distal tumors are frequently amenable
to transanal excision (Fig.25.10). The procedure
involves inltrating the submucosa with an epinephrine solution to minimize hemorrhage and
improve visualization during excision. The tumor
and a margin of normal mucosa are excised after
which the mucosal defect can be primarily closed,
marsupialized, or left open. Bleeding, stricture
and rectal perforation are the most commonly
reported complications. Recurrence rates range
from 4 to 36% [21, 22].
Circumferential rectal villous tumors are a
particularly challenging problem. Several authors
employ a sleeve mucosectomy to excise the
lesions [21, 22]. The mucosa is excised in a circumferential manner along the entire length of
the tumor. After the exposed muscular wall is
imbricated the proximal and distal mucosal margins are approximated (Fig. 25.11). Impaired
K. M. BullardDunn
Fig. 25.10 Transanal excision of rectal villous tumor.
Adapted from [17]
fecal continence occurred in 2 out of 12 patients
reported by Keck and colleagues and 8% of
lesions recurred [21].
The minimal access technique of transanal
endoscopic microsurgery is an option to manage
rectal villous tumors [23, 24]. A resectoscope
with light source and magnifying optics allows
COz insufation and overcomes the problems of
difcult exposure and poor light encountered
25 Rectal Polyps and Other Neoplasms
a
471
b
Fig. 25.11 Sleeve mucosectomy of a circumferential
rectal villous tumor. (a) Lesion and normal bowel circumferentially excised. (b) Muscle layer is imbricated to
with proximal rectal lesions. The equipment
expense, need for specialized training and length
of time required to perform these procedures are
some of the disadvantages of this technique.
Conversely, the technique allows direct access to
some proximal lesions, which would otherwise
c
reduce size of mucosal defect. (c) Mucosal defect is
closed following rectal mucosectomy. Adapted from [17]
require a laparotomy and anterior resection.
TAMIS uses laparoscopic instruments and a special access port. The technique is easier to learn
and results have been good [25, 26].
Posterior approaches to proximal rectal villous tumors have been reported [27, 28].
472
K. M. BullardDunn
However, most providers lack experience in these
approaches. This along with a high incidence of
incontinence and fecal stula are the major complications associated with this approach [29].
Another approach to rectal villous tumors not
amenable to transanal excision is low anterior
resection [30]. Mortality is 1–2% and recurrence
is very seldom reported. Numerous major potential morbidities include hemorrhage, anastomotic
leak, pelvic abscess, anastomotic stricture,
impaired continence, small bowel obstruction
and sexual and urinary bladder dysfunction.
For extremely low lesions coloanal anastomosis is used to restore intestinal continuity
[31]. Mortality rates are less than 4%, but again
morbidities include hemorrhage, anastomotic
leak, pelvic sepsis, small bowel obstruction and
sexual and urinary bladder dysfunction [32,
33]. Abdominoperineal resection (APR) is
reported in almost all large series of large rectal
villous tumors [34]. Because transanal procedures are effective and have low morbidity
rates, APR for the management of benign rectal
villous tumors of the rectum should be
extremely uncommon. In patients who are poor
candidates for coloanal anastomosis due to
poor sphincter function, a low Hartmann's procedure may be preferable to APR if an adequate
distal margin (1–2 cm) can be obtained, thus
avoiding the added potential morbidity of the
perineal wound. In addition, the above-mentioned abdominal approaches have mortality
and morbidity rates similar to APR.
Recurrence rates of 10–30% after transanal
excision or fulguration mandate close endoscopic
follow-up [21, 22]. If identied early, recurrent
lesions are managed by fulguration or local excision or, on occasion, proctectomy.
In summary, the authors treat benign rectal
villous tumors with transanal excision when possible. Patients who require rectal excision are
managed by anterior or low anterior resection.
Posterior approaches offer no advantage over
transanal or intraabdominal approaches. For
extremely large tumors that extend to the dentate
line coloanal anastomosis (with or without
colonic J pouch) is appropriate. Abdominoperineal
resection with an intersphincteric proctectomy or
a low Hartmann's procedure are reserved for
those patients who would be rendered incontinent by a low pelvic anastomosis.
Hyperplastic Polyps
Hyperplastic polyps (Fig. 25.12), sometimes
referred to as metaplastic polyps, are sessile
growths that are usually slightly paler in color than
the surrounding mucosa. Most hyperplastic polyps are less than 5.0mm in diameter, they can be
single or multiple and are invariably asymptomatic. Histologic examination reveals the crypts to
be elongated (Fig.25.11). The upper parts’ of the
crypts show papillary infoldings of normal-looking columnar, epithelial and goblet cells while the
lower parts of the crypts contain fewer goblet
cells. The cells are crowded together and project
into the lumen in folds or tufts. On cross section,
this distribution gives a characteristic stellate
branching appearance of the glands. These polyps
are generally regarded as the result of a disorder of
maturation of unknown origin. It should be noted
Fig. 25.12 Histology of juvenile polyp