Anal Intraepithelial Neoplasia (AIN)

Question 1

Def

Answer 1

Multifocal virally induced dysplasia of the perianal or intra anal epidermis which is associated with human papilloma virus (HPV
subtype 6, 11, 16, 18 – more commonly 16

Question 2

Risk Factors

Answer 2

• HPV infection (16 & 18) – a/w SCC
• HIV
• Anal Intercourse
• Immunocompromised patients
• History of genital intraepithelial neoplasia (VIN, CIN)
• History of extensive anogenital condylomata

Question 3

Grades

Answer 3

According to degree of dysplasia on biopsy – lack of keratocyte maturation and extension of proliferative zone from lower third (AINI) to full thickness of epithelium (AIN III)
- AIN I / Low Grade Squamous Intra-epithelial Lesion (LSIL) : raised, similar to Anal Condylomata but has ability to regress
- AIN II / High Grade Squamous Intraepithelial Lesion (HSIL)
- AIN III / HSIL : 10% will progress to anal carcinoma in 5 years, does not regress

Question 4

Clinical Presentation

Answer 4

• Symptoms: pruritus, pain, bleeding, discharge
• AIN I lesions: raised, similar to anal condylomata
• AIN III lesions: flat, may be white/grey/brown in colour
• Presence of ulceration will suggest progression to invasive anal carcinoma

Question 5

Treatment

Answer 5

• Patients will require HPV vaccination
• AIN III / HSIL: 6 monthly high resolution anoscopy (HRA) (using acetic acid / lugol iodine) + Local Ablation Therapy.
• Treatment involves topical immunotherapy, laser, cryotherapy, infrared coagulation and/or topical cytotoxic (i.e. 5-FU)