anal canal-anatomy, epidemiology, etiology, presentation, workup, staging

1. Carcinoma Anal Canal
Dr. MANISH DUTT
PG1st yr
(department of radiation oncology)

2. PREVIEW
• ANATOMY
• EPIDEMIOLOGY
• RISK FACTORS
• PATHOLOGY
• PRESENTATION
• DIAGNOSTIC WORKUP
• STAGING

3. ANATOMY
• Begins at anorectal
junction(palpable upper border
of anal sphincter)
• terminates at anal verge
• About 4 cm long
• Perianal skin-5cm radius
• Anal verge, dentate line, anal
columns, Hilton’s line
• Anal glands, anal crypts
• Surgical anal canal

4. relations
• In front- perineal body
1. In males- bulb of penis, spongy urethra
2. Female- lower part of posterior wall of
vagina
• Posteriorly- puborectalis muscle, coccyx
• Laterally-ischiorectal fossa
• External and internal anal sphinctors

5. sphincters
• Internal
1. inVoluntary sphincter
2. thickened extension of
circular muscle fibres
of rectum
3. Surrounds upper 3/4th
of anal canal
4. Internally the sphin. Is
separated from
mucous membrane
by internal venous
plexus
5. Nerve supply:
Sup.Hypogastric &
pelvic splanchnic
• External
1. Voluntary ,
2. Surrounds entire length of
anal canal
3. Divided into 3 parts
• Subcutaneous:
Flat band around anus
separated from perianal skin by
external venous plexus
• Superficial part:
Arises from tip of coccyx &
anococcygeal raphe, inserted into
perineal body
• Deep:
annular in shape
surrounds ano-rectal junction
No bony attachment – inserted
into perineal body

6. Arterial supply Venous drainage

7. Lymphatic drainage
• Anal canal superior to dentate
line- 2 pathways
1. Along the superior rectal vessels-
perirectal, presacral nodes
2. Along the middle rectal vessels-
internal iliac nodes (pudendal
and hypogastric nodes)
• Anal canal inferior to dentate
line (also the anal verge and anal
margin)- along the inferior
rectal vessels- superficial
inguinal, ext iliac

8. Internal sphincter
sympathetic (L-5) &
parasympathetic nerves (S-2, S-3, and S-4)
External sphincter
inferior rectal branch of the pudendal nerve
(S-2 ,S-3)
the perineal branch of S-4
Levator ani
sacral roots on its pelvic surface (S-2, S-3, and
S-4)
perineal branch of the pudendal nerve

9. EPIDEMIOLOGY
• 1% to 2% of all large bowel malignancies.
• 8,080 NEW CASES IN 2016.(0.5% of all) , 1080 deaths( 0.2% )(SEER statistics)
• New cases 1.8 per 100,000 men and women
• Median Age At Diagnosis is 61 yrs, median age at death was 65 years
• 5 yr survival is 66%
• Caucasian females -highest incidence rate (2.1 out of 100,000)
• Asian males had the lowest incidence rate (0.5 out of 100,000)
• African American males and Caucasian females had the highest mortality rate
(0.3 out of100,000 ), Asians lowest(0.1)
• According to the 2014 American Cancer Society statistics( ratio of almost 1:2
for men to women)
• incidence of anal cancer has been increasing over the last 30 years globally(
HPV/HIV)

11. INDIAN STATS
HIGHEST ASR –
• new delhi(0.7)
• Chennai(0.7)
• Nagpur (0.6)
• banglore(0.5)

12. RISK FACTORS
• HPV( 16>18)
• Homosexual men(15 times higher than heterosexual)
• women ->10 sexual partners , Receptive anal intercourse
• Vulvar , cervical dysplasia
• HIV( incidence twice,cd4<200, co-infection with HPV, early
recurrence)
• Smoking
• Immunosuppression
• AIN, SIL

13. PATHOLOGY- squamous or non squamous
• Classification of epidermoid
anal cancers on the basis of
morphologic :-
I. transitional cell carcinoma,
II. basaloid carcinoma, and
III. mucoepidermoid carcinoma.
• These tumors all arise from the
anal transition zone and are
often grouped together as
cloacogenic carcinoma.
• Other Precursor lesions- bowen
disease(I/E SCC), paget
disease(adenoca)
• WHO classification of malignant
epithelial tumors of the anal canal
includes :-
• squamous cell carcinoma,(75-80%)-
kerat/non kerat
• adenocarcinoma, rectal extensn, anal
glands)
• Melanoma( rare 1%)
• small cell carcinoma(endocrine cells)
• undifferentiated carcinoma.
• Lymphomas and sarcomas( very rare)

15. PRESENTATION
• SIGN & SYMPTOMS
• Bleeding(MC)45%
• Pain(2ND MC)30%
• sensation of a mass, itching, anal discharge, tenesmus,
incontinence/urgency
• sense of fullness or a lump in the anal canal
• enlarged inguinal lymph node
• 20% of patients are initially asymptomatic.

16. DIAGNOSTIC WORKUP
• HISTORY-
• high risk factors
• assessment of
anal sphincter
function
• h/o
inflammatory
bowel disease
• Gynaecological
history
• EXAMINATION
• DRE-
1. anal sphincter tone, clock location, distance from verge,
cicumferential involvement, size, superior extent
2. Fixation to the sphincter complex or adjacent organs such
as the vagina and prostate.
• PROCTOSCOPY-
1. Extent of mucosal spread, relationship to the dentate line,
2. facilitates biopsy
• Gynaecologic examntn- to rule out vaginal inv./ cervical
primary
• HIV testing and CD4 levels if indicated

17. • Routine investigations- CBC, LFT, KFT,
Chest X-ray
• Inguinal LN evaluation( 50% )- FNAC
/biopsy
• Sentinel node biopsy(86%success) role
still not established
• CECT chest+abdomen – to evaluate
distant disease and adenopathy
• CT pelvis or MRI pelvis- tumor size,
involvement of local structures( anal
sphincters, vagina or prostate), LN
assesment
• Endoanal ultrasound (optional )-
visualize perirectal nodes ,assess tumor
size, depth of invasion.

18. ROLE OF PET-CT
• Does not replace diagnostic CT, Routine use not validated
• as part of the staging evaluation in patients with T2-T4N0 disease or those with
involved lymph nodes
• valuable in detecting more extensive nodal and metastatic disease and detection
of synchronous malignancies(56% sensitivity, 90% specificity for LN)
• When compared to CT/ MRI upstaged patients in 20%, downstaged 25%, and
altered management in 37%.
• useful in the avoidance of unnecessary biopsies and surgery, with a negative
predictive value of 94%(Vercellino et al)
• prognostic value-significant correlation between metabolic response post-
treatment and progression-free as well as overall survival
• can also be used as baseline to gauge posttreatment response (Schwarz et al.
2008

20. STAGING
AJCC 2010
• Applies to all anal canal carcinomas (as per new WHO
classification) including Carcinomas, arise within anorectal
fistulas.
• Melanomas, carcinoids and sarcomas- excluded.
• Perianal skin and anal margin tumors (SCC, giant
condyloma/ verrucous carcinoma, basal cell ca, Paget`s
disease and Bowen`s disease)- staged as skin cancers

21. PROGNOSTIC FACTORS
• Male – poor prognosis
• Size- primary lesion <5cm more favourable
• Degree of differentiation- well differentiated tumors are more favourable
• Nodal status- N0- favourable
• Local extension- absence indicates better prognosis.
• HIV, low CD4 count- poor prognosis
• Low Hb, high WBC- poor prognosis
• increased p53 expression-lower locoregional control,
• lack of p21(CDK inhibitor) expression- poor prognosis