anal cancer

1. Epidemiology and classification
of anal cancer
Dr Touqeer A Siddiqui
MBBS MD FICM (MRCP) (UK)
Fellow medical oncology
Prince sultan military medical city

2. INTRODUCTION
• Anal cancer is uncommon. It comprises only 2.5
percent of all digestive system malignancies
• incidence -- increased over the last 30 years,
• female gender,
• infection with human papillomavirus (HPV),
lifetime number of sexual partners,
• genital warts, cigarette smoking, receptive anal
intercourse, and infection with human
immunodeficiency virus (HIV).

3. • Glandular,
• Transitional,
• Nonkeratinizing squamous
(proximal to distal,
respectively).
• Distally, the squamous mucosa
(which is devoid of epidermal
appendages such as hair
follicles, apocrine glands and
sweat glands) merges with the
perianal skin (true epidermis).
• This mucocutaneous junction
has been referred to as the anal
"verge" or margin.

4. Histology of anal cancer
• The anal canal has short zones covered with different
types of epithelium from proximal to distal end.
• Rectal zone with colonic type of mucosa
• Transitional zone varying with colonic mucosa and
squamous epithelium
• Squamous epithelium zone with non-keratinizing
squamous epithelium
• Perianal skin with keratinizing squamous cell
epithelium

5. • Two categories of tumors arise in the anal
region.
• Anal canal cancers
• Tumors that develop from mucosa (any of the
three types) .
• Perianal or anal margin cancers
• arise within the skin at or distal to the
squamous mucocutaneous junction

6. • Carcinoma in the anal canal generally originate
from the squamous epithelium in the distal part
of the canal, but can also originate from
cylindrical epithelium in the colonic mucosa or
perianal glands in the transitional zone.
• Most adenocarcinoma in the proximal zone will
be designated as distal carcinomas primary in the
rectum.

8. Anal canal tumors
• Squamous cell cancers — Tumors arising in the transitional
or squamous mucosa are squamous cell cancers and
appear to behave similarly, despite their sometimes
variable morphologic appearance
Basaloid features are identified in approximately 25 percent
of squamous cell cancers of the anal canal and must be
distinguished from basal cell carcinomas of the perianal
skin, which as noted below, are classified as skin cancers.
• Basaloid (also termed junctional or cloacogenic) carcinoma
is a variant of SCC that arises from epithelial transitional
zone.

9. • Tumors arising within the anal canal above the
dentate line are termed nonkeratinizing SCCs,
while those arising within the anal canal distal to
the dentate line are termed keratinizing SCCs.
• Adenocarcinomas — Adenocarcinomas arising
from glandular elements within the anal canal are
rare, but appear to share a similar natural history
to rectal adenocarcinomas, and are treated
similarly

10. Perianal skin cancers
• Tumors of the perianal skin are most often
SCCs but other types of cutaneous
malignancies (eg, basal cell carcinoma,
melanoma, Bowen's disease, extramammary
Paget disease) can arise within this region

11. Lymphatic drainage
• Lymphatic drainage of anal cancers is dependent
upon the anatomic site of origin
• Tumors originating above the dentate line, similar
to rectal cancers, drain to the perirectal and
paravertebral nodes.
• Tumors arising below the dentate line spread
primarily to the superficial inguinal and femoral
nodes, areas that are rarely involved by rectal
cancer

12. EPIDEMIOLOGY AND RISK FACTORS
• Sexual activity
• In a population-based, case control study of anal cancer,
women with anal cancer were more likely than controls to
have a history of genital warts (relative risk [RR] 32.5),
herpes simplex 2 (RR 4.1), or chlamydia trachomatis (RR
2.3), while men with anal cancer were more likely than
controls to have never been married (RR 8.6), to have
engaged in homosexual sexual activity (RR 50), to have
practiced receptive anal intercourse (RR 33), and to have a
history of genital warts (RR 27) or gonorrhea (RR 17) [36].
Subsequent studies confirmed the relationship between
anal cancer and receptive anal intercourse in men

13. EPIDEMIOLOGY AND RISK FACTORS
• Human papillomavirus infection
• Human papillomavirus (HPV) infection is the most
commonly diagnosed sexually transmitted disease in the
United States and provides as least part of the link between
sexual activity and anal cancer.
• A close association exists between infection by oncogenic
HPV strains and many premalignant and malignant lesions
of the genital tract, anus, and rectum
Furthermore, HPV infection is the common link that explains
the association between index and second primary
anogenital cancers and oral cavity/pharyngeal cancers

14. • HPV DNA has been isolated from 46 to 100
percent of in situ and invasive SCCs of the
anus , and epidemiologic studies have shown
that up to 93 percent of anal SCCs are
associated with HPV infection.
• Women are more likely to have HPV
associated anal cancer than are men

15. • HIV infection
• the overall impact of HIV infection on
incidence rates of anal cancer remains unclear
since population-based studies have produced
conflicting results

16. • The incidence of HPV infection and HPV
associated preinvasive and invasive malignancy is
increased in HIV-infected patients, regardless of
sexual practice
• In a meta-analysis of 53 studies, the prevalence
of both high-risk anal HPV subtypes (74 versus 34
percent) and anal cancer (45.9 versus 5.1 per
100,000 men) was significantly higher among
HIV-positive as compared to HIV-negative MSM

17. • Chronic immunosuppression not due to HIV —
• Other causes of chronic immunosuppression, such as solid
organ transplantation, also may be associated with the
development of high grade AIN and invasive anal
carcinoma.
• Among renal transplant recipients, for example, the risk of
anogenital cancer may be increased as much as 100-fold;
• Risk has been associated with persistent HPV infection .
AND chronic glucocorticoid therapy

18. • Cigarette smoking —
• Several case-control studies have noted a
statistically significant risk of anal cancer in
smokers
• is thought to act as a co-carcinogen

19. • THANKS