Anal Cancer
Background
What is the incidence of anal cancer in the U.S.?
5,290 cases/yr in 2009 in the U.S. (ACS 2009)
Is there a gender predilection for anal cancer?
Yes. Anal cancer is more common in females than males (2:1).
What are some risk factors for anal cancer?
Hx of STDs/anal warts; multiple sexual partners (>10); anal-receptive intercourse; immunodeficiency (HIV, solid organ transplantation); smoking; Hx of cervical, vulvar, or vaginal cancer
Is anal cancer an AIDS-defining illness?
No. However, cervical cancer is an AIDS-defining illness.
What is the predominant histology of anal cancer?
Squamous cell carcinoma (75%–80%) is the predominant histology.
What virus strains are strongly associated with anal cancer?
HPV strains 16, 18, 31, 33, and 35 are strongly associated with anal cancer.
How long is the anal canal, and where does it extend?
The anal canal is 4 cm long, extending distally from the anal verge (palpable junction between the internal sphincter and subcutaneous part of the external sphincter) to the anorectal ring (where the rectum enters the puborectalis sling) proximally.
What is the histopathologic significance of the dentate line (aka pectinate line)?
The dentate line is the anatomic site where mucosa changes from nonkeratinized squamous epithelium distally to colorectal-type columnar mucosa proximally (dividing the upper from the lower anal canal).
Describe the anatomic location of the anal verge.
The anal verge is located at the junction of nonkeratinized squamous epithelium of the anal canal and keratinized squamous epithelium (true epidermis) of perianal skin.
Which site carries a better prognosis: the anal margin or anal canal?
The anal margin carries a better prognosis.
Which pathology carries a higher risk for local and distant recurrence?
Adenocarcinoma carries a higher risk.
What is the significance of the dentate line in terms of LN drainage?
Above dentate line: drains to pudendal/hypogastric/obturator/hemorroidal → internal iliac nodes
Below dentate line: drains to inguinal/femoral nodes → external iliacs
What % of anal cancer pt present with +LNs?
25%–35% of these pts present with +LNs.
What are the 2 most common sites of DM?
Liver and lung
What is the occult positivity rate for inguinal nodes (i.e., if clinically−) in anal cancer?
For inguinal nodes, the occult positivity rate is 10%–15%.
What is the rate of extrapelvic visceral mets at presentation for anal cancer?
Extrapelvic visceral mets are present in 5%–10% of pts.
In anal cancer, what % of clinically palpable LNs are actually involved by cancer?
50% of clinically palpable LNs involve cancer, while the other 50% are usually reactive hyperplasia.
In anal cancers, what are the most important prognostic factors for LC and survival?
Tumor size and DOI predict for LC. The extent of inguinal or pelvic LN involvement predicts for survival.
Workup/Staging
What are 4 common presenting Sx in anal cancer?
Bleeding, pain/sensation of mass, rectal urgency, and pruritus
What does the workup for anal cancer pts include?
Anal cancer workup: H&P (including gyn exam for women with cervical cancer screening), labs (HIV if risk factors), imaging, Bx of lesion, and FNA of suspicous LN
What imaging studies are typically done for anal cancer pts?
Transanal US (to assess for perirectal nodes/assess invasion), CXR or CT chest, CT abdomen/pelvis, and PET/CT
What features of anal lesions need to be appreciated on physical exam? Why?
The degree of circumferential involvement and anal sphincter tone should be appreciated, as these may dictate Tx.
What is the approach to suspicious inguinal LNs in anal cancer pts?
FNA Bx should be performed for suspicious inguinal LNs.
On what is the T staging for anal cancer based? Define T1-T4.
T staging for anal cancer is based on the size of the lesion.
T1: ≤2 cm
T2: >2–5 cm
T3: >5 cm
T4: invasion of adjacent organs (vagina, urethra, bladder)
Does tumor invasion of sphincter muscle by anal cancer constitute a T4 lesion?
No. Direct invasion of the rectal wall, perirectal skin, subcutaneous tissue, or sphincter muscle are not classified as T4.
Most pts with anal cancer present with what T stage?
Most anal cancer pts present at stage T2 or T3.
What is the N staging of isolated perirectal nodal involvement in anal cancer?
Isolated perirectal nodal involvement is staged as N1.
What is the N staging of unilat inguinal or internal iliac LNs in anal cancer?
Unilat inguinal or internal iliac LNs are staged as N2.
What N stage is an anal cancer pt with both perirectal and inguinal LNs?
Perirectal and inguinal LNs reflect stage N3.
What N stage is an anal cancer pt with bilat inguinal or internal iliac LNs?
Bilat inguinal or internal iliac LNs reflect stage N3.
What anal cancer pts have AJCC stage III Dz?
Node+ or T4 pts have AJCC stage III Dz.
What is the AJCC 7th edition (2009) stage grouping for anal cancer?
Stage I: T1N0
Stage II: T2N0 or T3N0
Stage IIIA: T1-3N1 or T4N0
Stage IIIB: T4N1 or TXN2 or N3
Stage IV: TXNXM1
What are the 5-yr OS and LR rates after surgical resection alone for anal cancer?
The 5-yr OS rate after complete surgical resection is ~70%, and the LR rate is ~40%. (Mayo review of 118 pts: Boman BM et al., Cancer 1984)
What % of pts who relapse develop local recurrent Dz as part of the total failure pattern?
~80% develop local recurrent Dz. (Boman BM et al., Cancer 1984. Note: This was also a surgical series.)
Related posts:
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
