Anal Malignancies

Question 1

Classifications

Answer 1

• Anal margin (distal to dentate line*) vs. anal canal (proximal to dentate line)
• Perianal vs. intra-anal (cannot be visualized with gentle eversion of buttock)

Question 2

Types of malignancies

Answer 2

• Epidermoid Carcinoma – (i.e. SCC most common)
• Adenocarcinoma
• Melanoma (1%) - lesion may mimic a thrombosed external hemorrhoids
• Lymphoma / Sarcoma

Question 3

Risk factors

Answer 3

• HPV infection (16 & 18) – a/w SCC
• HIV
• Anal Intercourse (33 x increased risk)
• History of genital warts

Question 4

Clinical Presentation

Answer 4

1. Pain and Bleeding
2. Anal Mass
3. Pruritis and Discharge
4. Fecal Incontinence
5. Recto-vaginal fistula (females)

Question 5

DRE Findings

Answer 5

• Anal margin tumours will appear as malignant ulcers,
• Anal canal tumours tend to be palpable as irredular indurated tender ulceration.
• Always do DRE to assess for sphincter involvement

Question 6

Mode of Spread

Answer 6

• Anal canal cancer spreads locally in a cephalad/upwards direction, outwards into the anal sphincter and into the rectovaginal
  septum, perineal body, scrotum or vagina.
• Lymph node metastases occur frequently starting from perirectal group then to inguinal, hemorrhoidal and lateral pelvic lymph
  nodes. (i.e. 30% inguinal LN spread with tumour size > 5cm)

Question 7

Investigations

Answer 7

• Examination under anesthesia (EUA) with biopsy of the anal mass for histological diagnosis (allows assessment of tumour, involvement of adjacent structures and nodal involvement)
• MRI of pelvis for loco-regional staging
• CT TAP or PET-CT to stage for metastatic disease
• Biopsy or FNAC of groin nodes (if radical block dissection is contemplated) - although 1⁄3 of patients will have enlarged inguinal
  lymph nodes only 50% will have confirmed metastatic spread
• Stage is based on AJCC TMN staging 7th edition

Question 8

Treatmetn

Answer 8

• Chemoradiotherapy with 50.4Gy radiotherapy in 28 daily fractions with mitomycin C and 5FU (Nigro protocol).
• For all T2-T4 tumours, prophylactic low dose radiotherapy to clinically uninvolved lymph nodes (reduce risk of recurrence)
• Surgery I
  ● ● ● ●
  Examination under anesthesia to confirm diagnosis and assess extent of disease involvement,
  Local excision for small T1 (<2cm) tumours,
  Defunctioning stoma prior to commencement of oncological treatment.
  Salvage APR with end colostomy and myocutaneous flap is considered (if disease still present after chemoradiotherapy