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20 Anal Cancer
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Those patients with isolated inguinal nodal recurrence
represent a distinct subset of metastatic disease that may be
considered for resection with intent to cure. It is possible to
have a complete clinical response at the primary site with an
isolated inguinal metastasis amenable to supercial inguinal
groin dissection. If there is no evidence of additional distant
or regional disease on re-staging studies (contrast CT of the
chest, abdomen, and pelvis and/or PET-CT), patients with
isolated inguinal metastases can be considered for supercial
inguinal lymph node dissection, typically followed by systemic therapy. FNA of the area to conrm the diagnosis of
SCCa is important, as morbidity of groin dissection can be
substantial. Although complication rates for groin dissection
following radiation are fairly high (wound dehiscence, surgical site infection, edema), long-term outcomes from smaller
studies suggest that it is reasonably effective in treating isolated locoregional recurrent disease. 5-year DFS rates of
55% have been observed in select patients meeting criteria
for resection [48].
Anal Cancer andHIV
Patients living with HIV (PLWH) have a higher incidence of
anal cancer and comprise a known high-risk group.
Comparisons of the PLWH population with HIV-negative
cohorts have been mostly from larger database studies but
have conrmed that 5-year OS and rates of complete response
are similar [59, 60]. Other studies examining treatment
course and tolerance between PLWH and HIV-negative
patients found that treatment paradigms used were the same
and there was no difference in tolerance or toxicity of chemoradiation. Some small retrospective studies seem to indicate
that radiation-related morbidity in the form of skin inammation and pain may be greater in the immunocompromised
[60]. NCCN Guidelines for Cancer in PLWH state that
PLWH who have anal cancer should be treated as per guidelines used for HIV-negative patients and that modications
to treatment should not be made solely on the basis of HIV
status [49]. Use of normal tissue-sparing radiation techniques (IMRT) and consideration of nonmalignant causes for
lymphadenopathy may deserve more attention in this cohort
along with the need for more frequent post-treatment surveillance anal examinations.
Surveillance
Follow-up of patients after treatment of primary anal canal
or perianal cancer is essential. Initial physical examination
is typically done 8–12 weeks following the last dose of
radiation. Examination of the anal canal or perianal area by
digital rectal exam and direct visual inspection of the area
by anoscopy (if the lesion originally extended into the anal
canal) should be performed. Careful documentation of the
extent of the response should be made. It is often helpful to
include a digital photograph of the tumor/tumor treatment
site in the electronic medical record, both at initial diagnosis and at surveillance examinations, as subtle changes in
the tumor treatment site may be the rst sign of persistence/
recurrence, and examiners may change with time. The
rationale for waiting for 6 months to perform biopsy in
patients whose tumors are stable or regressing is that the
ionizing effect of radiation on tumor cells extends well into
the post-treatment period. The data to support this strategy
comes from observational studies and the ACT II trial. The
ACT II study compared the use of either mitomycin or cisplatin for anal cancer and showed that there was no difference in either OS or PFS between the two drugs. It did
show, however, that up to 72% of patients who failed to
show a complete response at 11 weeks did respond completely by 26 weeks with no evidence of residual visual evidence of tumor, ulceration, or mass present [35]. Routine
biopsy is not indicated in the absence of a mass or ulcer.
However, as noted above, patients who have an enlarging
mass or other evidence of progression on physical examination should have a biopsy at the time that progression is
noted and the histologic results interpreted in the context of
the clinical situation.
It is recommended that contrast CT scan of the chest,
abdomen, and pelvis be performed annually for 3 years for
those with large or clinically node-positive tumors. Digital
rectal examination with anoscopy and inguinal nodal palpation should be done every 3–6 months for 4–5 years [49].
Anal Adenocarcinoma
Anal adenocarcinoma differs from rectal adenocarcinoma
inlocation and prognosis. It is often difcult to differentiate
between a distal rectal tumor invading the anal canal and a
primary anal adenocarcinoma (Fig. 20.5). The latter typically present with a mass in the anal canal with a minimal
mucosal component. Mucoid discharge is a frequent complaint. Anal adenocarcinoma can arise directly from an anal
gland or can be found in proximity to chronic stula tracts,
particularly in patients with Crohn’s disease, which can present diagnostic challenges leading to delays in diagnosis [61].
Anal adenocarcinoma accounts for approximately 20% of all
anal cancers [62]. They may appear morphologically similar
to rectal adenocarcinoma but will have an increased risk of
inguinal lymph node metastasis [63].
Anal adenocarcinomas are both staged and treated similarly to rectal cancers. Large prospective series are lacking
due to the rarity of the disease, but neoadjuvant radiotherapy
or chemoradiotherapy prior to APR has been associated with
366
Fig. 20.5 Anal adenocarcinoma with left inguinal lymph node
positivity
improved disease-free survival and local control as compared to upfront surgery [64, 65].
Comparing the frequency and survival of anal adenocarcinoma to that of rectal adenocarcinoma and anal squamous
cell carcinoma, it is noted that both the frequency and overall
survival for anal adenocarcinoma are lowest. Comparisons
of survival (all stages) in 57,369 cases of anorectal cancer
revealed that anal adenocarcinoma represented only 0.8% of
cases with a mean survival of 33 months, compared to rectal
adenocarcinoma representing 87.8% of cases with a mean
survival of 68 months and SCCa representing 11.4% of cases
with a mean survival of 118 months [66]. A study using the
National Cancer Database revealed that patients with anal
adenocarcinoma had statistically worse survival when compared to both rectal adenocarcinoma and anal squamous carcinoma. Decreased survival in the anal adenocarcinoma
group was associated with proctectomy and the use of chemotherapy, most likely reecting more advanced disease at
diagnosis [67]. It should be remembered, however, that studies of anal adenocarcinoma are hampered by accuracy of
diagnosis, as it is often extremely difcult to distinguish
whether a patient has true anal versus distal rectal
adenocarcinoma.
Verrucous Carcinoma
Verrucous carcinomas of the anus are also known as BuschkeLowenstein tumors. It was rst described by Buschke and
Lowenstein in 1925 and is also known as giant condylomata
[68]. It presents as a large exophytic cauliower-like lesion
on the perianal skin. These lesions are characterized by their
large size and their ability to inltrate surrounding tissues
(Fig.20.6). There has been controversy as to whether a true
D. R. Sands and N. N. Mahmoud
Fig. 20.6 Verrucous anal carcinoma with locally invasive histologic
features. (Reused with permission from Pathology Outlines. ©
Copyright PathologyOutlines.com, Inc. www.PathologyOutlines.com)
Buschke-Lowenstein tumor should be considered benign
and dened by its lack of invasion of the basement membrane (giant condylomata) or should be considered a slowly
growing squamous cell carcinoma with tendency toward
local invasion [69]. The lack of clarity in the denition has
hampered scientic study. These tumors are often associated
with HPV types 6 and 11 [70]. Following excision, substantial local recurrence rates of over 50% have been reported in
meta-analysis [71]. Malignant transformation has been
reported in 40–60% of cases [72]. The average time to transformation to malignancy is approximately 5 years following
initial diagnosis [71].
Wide surgical excision is the mainstay of treatment.
Chemoradiation, laser therapy, photodynamic therapy, antiretroviral therapy, and intralesional injection have all been
reported with less success than local excision [73–76]. If
mesorectal lymph node metastasis is suspected or there is
local destruction of the anal canal, a more aggressive
approach to treatment that may include chemoradiotherapy
and/or abdominoperineal resection may be indicated.
Melanoma
Melanoma of the anus is a rare and aggressive tumor. First
described in 1857 by Moore [77], the reported incidence of
mucosal melanoma is between 1% and 2% of all melanomas
affecting approximately 2 per million persons per year [78].
It has been estimated that anal melanoma accounts for 0.05%
of all colorectal malignancies diagnosed each year [79].
Anal melanoma is most commonly seen in the sixth
decade of life, with a female predominance [80]. It is unclear
if the poor prognosis is related to biologic factors or simply
late stage at diagnosis. As with other tumors of the anal
region, patients will often attribute their symptoms of bleed-
20 Anal Cancer
367
ing and pain to hemorrhoids, thereby delaying diagnosis. A
pigmented ulcerated mass in the region enhances the suspicion of melanoma (Fig.20.7); however, it is recognized that
up to 30% of anal melanomas are amelanotic [81]. These
tumors can be found incidentally in hemorrhoidectomy specimens, and this scenario is one of the rare times when the
tumor may be curable.
The extent of disease is assessed with pelvic MRI,
PET-CT scan, colonoscopy, and complete dermatologic and
ophthalmologic examination. The use of sentinel lymph
node mapping is controversial with unproven survival benet. The nodal basin is variable in the inguinal region and can
be either unilateral or bilateral. While hematologic spread
occurs, lymphatic spread to mesorectal nodes is not uncommon [82].
There is no TNM staging system specically for anorectal
melanoma. The staging for anorectal lesions has historically
been based on clinical ndings: stage I and II, local disease;
stage III, regional lymph node involvement; and stage IV, distant metastatic disease [83]. Based on the ndings that depth
of muscle penetration impacts survival, a newer staging classication was proposed by Falch etal. (Table20.5) [84].
The treatment for anorectal melanoma has historically
been abdominoperineal resection. However, many studies
have shown no survival benet for this procedure compared
to wide local excision, and it is recognized that most, but not
all, treatment failures are from distant metastatic disease
[85–87]. There is, however, improved local control with
APR compared to wide local excision in some studies, and
the use of APR for larger lesions or for salvage and palliation
can be considered in select cases. The addition of radiotherapy has been proposed to augment local control after wide
local excision, but it is not routinely used, as melanomas are
not considered radiosensitive tumors [88, 89]. A study of 570
patients who underwent surgical resection (67% wide local
excision vs 33% APR) showed that the 5-year overall survival was 21% in both groups regardless of the ability to
achieve an R0 resection [90]. Similarly, a review of 653
patients with anal melanoma found comparable overall survival in both the radical and local excision groups [91]. These
dismal statistics speak to the fact that death from anal melanoma is most frequently caused by the presence of distant
metastatic disease, not from failure of local control.
Molecular diagnostic testing has gained importance in the
characterization and management of anal melanoma. The
mutations which are most commonly tested are BRAF and
c-KIT. BRAF mutations may direct therapy with BRAF
inhibitors in cutaneous melanomas [92]. Tyrosine kinase
inhibitors such as imatinib have been targeted for treatment
of patients with c-KIT (+) mutations [93].
Perianal Paget’s Disease (Intraepithelial Adenocarcinoma)
Fig. 20.7 Histology of anal melanoma
Table 20.5 Staging classication of primary anorectal malignant
melanomas
Stage Tumor spread
I Local tumor spread without inltration of the muscular layer
II Local tumor spread with inltration of the muscular layer
III Regional tumor spread and/or positive lymph node
metastasis
IV Disseminated tumor spread
Extramammary perianal Paget’s disease, or intraepithelial
adenocarcinoma, was rst reported in 1889 [94]. It is a rare
skin condition arising from the apocrine glands, frequently
presenting as a scaly lesion on the perianal skin (Fig.20.8).
It is estimated that 6% to 20% of all cases of extramammary
Paget’s disease occur in the perianal region [95–97]. It is
more common in women with incidence rising starting in the
fth decade [98]. The lesion can be weeping and ulcerative
and accompanied by bleeding pruritus or pain. Misdiagnosis
as other more common skin conditions is not unusual, with
biopsy prompted only after failure of topical steroid treatment [99]. Three types of extramammary Paget’s disease
have been described: those with no associated malignancy,
those associated with an apocrine tumor in proximity, and
those associated with internal gastrointestinal or genitourinary malignancy. This underscores the importance of a thorough search for associated malignancies [100]. In a recent
review of 108 patients with anal Paget’s disease, the rate of
colorectal adenocarcinoma was 18.5% [101].
Histopathologic diagnosis is conrmed with the ndings
of classic Paget’s cells with abundant cytoplasm, prominent
nucleoli, and pleomorphic nuclei (Fig. 20.9) [102]. The
surrounding keratinized cells are compressed.
Immunohistochemical staining for cytokeratins, mucins,
Left
Dentate line
368
Fig. 20.8 Paget’s disease of the anus. (Reuse with permission from
Kann [127])
Fig. 20.9 Histology of anal Paget’s disease
gross cystic disease uid protein, and carcinoembryonic
antigen has all been utilized in the diagnosis. Epidermal
disease does not invade the dermis, while intradermal
D. R. Sands and N. N. Mahmoud
Posterior
Anal
margin
Anal verge
Right
Anterior
Fig. 20.10 Biopsy mapping chart of anal Paget’s disease
growth pattern is less common [99]. Primary extramammary Paget’s disease is thought to result from carcinoma in
situ of the apocrine gland ducts, whereas secondary Paget’s
is thought to arise from intraepithelial spread of underlying
carcinoma [103]. Because the incidence of extramammary
perianal Paget’s disease is so low, the majority of the literature is comprised of case reports or retrospective reviews of
small series ranging from 20 to 108 cases reported sporadically over a span of decades [99, 101, 104–106]. This haphazard reporting has created dilemmas in treatment because
of lack of standardization or contribution of prospective
studies.
Achieving adequate surgical margins is a challenge in
perianal Paget’s disease because it is hard to detect grossly.
Histologically, the disease can be present in normalappearing surrounding tissues due to the multifocal or projection like growth pattern. The anatomic constraints of the
anal canal can preclude adequate local excision of lesions
that extend proximally. Mapping biopsies of the perianal
region have been shown to be useful in avoiding overtreatment and achieving clear margins (Fig.20.10) [102, 107].
Depending on the extent of excision, reconstruction may be
necessary with skin grafts or aps and may require a temporary diversion for proper healing. Mohs surgery with repeated
frozen section analysis at a single setting has been used as a
tool to tailor the excision with appropriate pathologic margins, but exposure is challenging, and the length of time it
takes to perform the surgery in the prone or lithotomy position may limit the utilization of this technique [102]. The
central focus of treatment is wide local excision with clear
margins. However, if clear margins cannot be obtained in the
anal canal with preservation of sphincter integrity or there is
an associated malignancy in the anus or rectum, an abdominoperineal resection may be necessary.
20 Anal Cancer
Table 20.6 Classication and treatment of extramammary Paget’s disease
Stage Description Management
I Epidermal/intradermal Paget’s cells found in perineal, scrotal, or
vulvar area
IIA Epidermal/intradermal Paget’s disease with involvement of anal canal WLE plus transanal resection
IIB Epidermal/intradermal Paget’s with synchronous malignancies Treat malignancy accordingly (e.g., abdominoperineal
III Epidermal/intradermal Paget’s with node involvement (inguinal, iliac) Chemotherapy
IV Paget’s disease with distant metastases of associated carcinoma Chemotherapy, radiotherapy, local palliative management
WLE wide local excision, MMS Mohs micrographic surgery, TSE traditional surgical excision
WLE/MMS/TSE; if not amenable to resection or patient
refusal of surgical treatment, consider 5% imiquimod
resection for rectal malignancy)
369
Due to the morbidity associated with local excision and/
or abdominoperineal resection, other strategies have been
employed in the management of extramammary perianal
Paget’s disease with variable success. The use of topical
imiquimod has been reported [100, 108]. Treatment with
radiation therapy has been reported for primary and recurrent
disease. The majority of the published studies are case
reports or very small series precluding guiding conclusions
as to efcacy. While there is no standardized treatment algorithm, nonsurgical treatments avoiding disguring surgical
excision may be effective in select cases [109–111].
Photodynamic therapy has been utilized to avoid surgical
resection [112]. In one of the largest series of patients with
Paget’s disease reported, however, recurrence rates were
substantial. Half of the patients with invasive and one fourth
of those with noninvasive Paget’s disease recurred after complete resection, underscoring the rationale for exploring
other nonsurgical treatments for this disease [106]. Moller
etal. proposed a classication and treatment scheme based
on stage of disease (Table20.6) [113].
Basal Cell Carcinoma
Basal cell carcinoma is the most frequent malignant neoplasia of the skin, compromising 75% of nonmelanocytic
tumors [114]. Tumors arising in non-sun-exposed areas are
rare. As one might expect, perianal basal cell carcinoma is
very rare, representing 0.1% of all basal cell tumors and
0.2% of all perianal tumors [115]. There has been association of these tumors with synchronous lesions in other locations in the body [116]. Therefore, a thorough examination
of the entire skin surface should be performed. These tumors
have no association with HPV. Treatment is local surgical
excision with negative margins.
Gastrointestinal Stromal Tumor (GIST)
Gastrointestinal stromal tumors are the most common mesenchymal tumors of the GI tract, most often located in the
stomach and small bowel [117]. The interstitial cells of
Cajal are the cells of origin for these tumors [118].
Anorectal GISTs account for only 5% of all GISTs, with
those located in the anal canal comprising only 2% of this
subgroup [119]. There is a male predominance, with diagnosis typically in the sixth to seventh decade [119]. The
tumor presents as a well-circumscribed hypoechoic mass in
the intersphincteric space, as seen on endoanal ultrasound
[117]. On physical exam, these lesions can present as
entirely submucosal or as an ulcerated mass with a large
non-luminal, submucosal component. Evaluation of proximity to adjacent structures like the vagina or prostate
should be done. Biopsy is appropriate if the mass is larger
and ulcerated as a chemotherapy neoadjuvant approach
may be benecial. Diagnosis with endoanal ultrasound or,
more commonly, MRI for locoregional staging is appropriate, with a CT scan of the chest, abdomen, or pelvis or a
PET-CT providing distant staging information. Because
spread of these mesenchymal tumors is mostly hematogenous, GISTs rarely spread to locoregional lymph nodes
[120]. Surgical excision is the mainstay of treatment for
smaller tumors. Targeted therapy with tyrosine kinase
inhibitors such as imatinib (Gleevec©) is often performed
to reduce the size of larger, ulcerated, or high mitotic GIST
tumors to facilitate local resection in those tumors that are
proto-oncogene c-KIT (CD117) positive [121]. It has been
suggested that low-risk GISTs with a diameter <2cm and
mitosis <5 per 50 per high-powered eld may be considered for local excision if sphincter-saving surgery is technically feasible with or without preoperative tyrosine kinase
inhibitor treatment (Fig. 20.11a, b). There are few large
case series analyzing treatment for anal GIST.One of the
larger reports of 18 patients noted local recurrence in 6 of
10 patients treated with local excision compared to none of
the 8 patients treated with radical surgery. There was, however, no difference in survival in the two groups [122].
Evidence suggests that GISTs that are more aggressive
should be treated with radical excision as well as chemotherapy [123]. Long periods of latency, exceeding 10 years,
between initial treatment and development of recurrence,
either local or distant, have been reported [119, 123, 124].
This underscores the potential benet of extended surveillance of these patients.
370
ab
Fig. 20.11 Gastrointestinal stromal tumor (GIST) of the anus. (a) Histologic appearance of GIST tumor. (b) Small submucosal non-ulcerated
GIST tumor. (Reused with permission from Author Azzaza etal. [117]. Copyright Elsevier)
D. R. Sands and N. N. Mahmoud
Conclusion
In conclusion, malignancies of the anus are diverse and relatively rare, but the overwhelming majority of cancers are
squamous cell carcinomas. These cancers are increasing in
incidence but are imminently curable at early stages and
amenable to early detection. Most, but not all, are HPV
mediated and thus may be preventable. Protocols for treatment of anal squamous cell carcinoma, both in the anal canal
and perianal region, are well-studied, and patients typically
enjoy favorable outcomes. A high index of suspicion for anal
cancer when persistent anorectal symptoms occur and a willingness to quickly examine and biopsy suspicious lesions
may limit morbidity and mortality from both anal squamous
cell carcinoma and in those anal cancers that are less common and more lethal.
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Presacral Tumors
ScottR.Kelley andEricJ.Dozois
21
Key Concepts
• The presacral (retrorectal) space is the location of a wide
range of rare tumors with incidence as low as 1in 40,000–
60,000 hospital admissions. Discovery in asymptomatic
patients is increasing due to expanded use of crosssectional imaging.
• Advances in cross-sectional imaging and understanding
of tumor biology have led to better outcomes for these
challenging patients.
• MRI is the best imaging study to assist in diagnosis and
operative planning.
• Most benign lesions have malignant potential and observation alone in some patients is acceptable when a dedicated surveillance protocol is in place.
• When performed appropriately and selectively, a CTguided biopsy of the lesion may assist in management of
solid and heterogeneous cystic lesions.
• The surgical principles that should guide a surgeon who
manages these lesions are a function-sparing approach for
benign lesions and an en bloc approach for malignant
lesions.
Introduction
The presacral (retrorectal) space is a potential space and the
location of a wide range of rare tumors. Reports from referral
centers have indicated the incidence may be as low as 1in
40,000–60,000 hospital admissions [1–4]. Detection is fre-
Supplementary Information The online version of this chapter
(https://doi.org/10.1007/978- 3- 030- 66049- 9_21) contains supplementary material, which is available to authorized users.
S. R. Kelley (*) · E. J. Dozois
Mayo Clinic, Division of Colon and Rectal Surgery,
Rochester, MN, USA
e-mail: kelley.scott@mayo.edu
quently delayed since patients are often asymptomatic until
tumors reach considerable size. Advances in cross-sectional
imaging and understanding of tumor biology have led to better outcomes for these challenging patients. Although most
surgeons will encounter a patient with a presacral tumor in
their career, few will have the opportunity to treat a large
volume of these complex lesions. The care of these patients
can be greatly optimized by an experienced multidisciplinary
team (MDT).
Anatomic Considerations
Evaluation and management of presacral tumors require a
thorough understanding of the anatomic relationships of the
pelvic viscera, the bony connes of the pelvis, and the neuromuscular structures. Anteriorly the presacral space is bordered by the mesorectum, posteriorly by the anterior table of
the sacrum, inferiorly by the levator muscles, and laterally by
the lumbosacral plexus, ureters, and iliac vessels (Fig.21.1).
Several important vascular and neural structures are
located where presacral tumors occur. Injury to these may
have important physiological, neurologic, and musculoskeletal consequences. Knowledge of anatomy of the thigh and
lower extremity is also necessary in complex cases utilizing
muscle or other soft tissue ap coverage. When sacrectomy
is required, a multidisciplinary surgical team familiar with
the anatomy of the sacrotuberous and sacrospinous ligaments, sciatic nerve, piriformis muscle, the thecal (dural)
sac, and sacral nerve roots is necessary (Fig.21.2a and b).
Knowledge of sacral nerve root function is important in
order to be able to counsel patients on potential functional
sequelae that can inuence their quality of life. Todd and colleagues evaluated bowel and bladder function in a group of
patients following sacral resection. They found that if bilateral S2–S5 nerve roots were removed patients had complete
loss of bladder and bowel function. If bilateral S3–S5 were
removed, 40% had normal bowel function and 25% had nor-
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375