Anal Intraepithelial Neoplasia (AIN) is a precancerous skin change in the perineal region caused by HPV (human papillomavirus) exposure. Anal intraepithelial neoplasia (AIN) refers to the premalignant dysplasia of the anal epithelium, which is caused by infection with the human papillomavirus (HPV). It takes the form of anal cancer over time, necessitating chemo-radiation and maybe surgery.
AIN is a condition in which the lining of the anus contains abnormal cells. Although the cells are not cancerous, they can become cancerous in the future. The most prevalent pattern of cancer spread is anal border tumors spreading to the inguinal lymph nodes, whereas more distal cancers travel to the pelvic lymph nodes. The majority of AIN cells originate in the skin surrounding the perianal skin, although they are also found inside the anal canal.
There are various levels of AIN. Each grade is determined by the thickness of the skin’s surface layer which is impacted by the abnormal cells. The different grades of AIN are as follows:
- AIN 1: It indicates that the aberrant cells are located in the lowest one-third of the skin that covers the anus.
- AIN 2: In this grade, the aberrant cells reside in the lowest two-thirds of the skin.
- AIN 3: It indicates that the abnormal cells have invaded the entire thickness of the anus’ skin.
AIN is serious problem because, in some situations, it can progress to anal cancer. Before developing cancer, AIN goes through three phases (Grade I, Grade II, and Grade III) when examined under a microscope. As compared to grade 1 and grade 2 AIN, grade 3 AIN increases the risk of developing cancer. The diagnosis of AIN1,2,3 is made with the help of cytology or biopsy during routine checkups. The nucleus-to-cytoplasm ratios can then be used by a pathologist to review and classify cells. The progression of AIN to cancer is determined through the high or low-grade classification.
AIN (Anal Intraepithelial Neoplasia) Symptoms
AIN is mostly discovered in warts and other benign skin tags/hemorrhoids, as well as lesions in the anal canal and on the skin around the anus. Anal discomfort and bleeding are the most prevalent symptoms of AIN. Other signs and symptoms include:
- A tangible mass
- Roughening and thickness of the skin.
- Lumps and ulcers on the skin.
- Incontinence of faeces.
- Palpable inguinal nodes.
The other important medical history that is required for the diagnosis of the AIN include:
- HPV infection status and vaccination record.
- History of HIV infection and testing.
- Anal trauma history.
- Familial colorectal cancer.
AIN (Anal Intraepithelial Neoplasia) Causes
Clinical variables and behaviors linked to the development and retention of human papillomavirus (HPV) infection are possible causes of AIN and anal cancer.
Since AIN and anal cancer are closely linked to HPV infection, behaviors that are responsible for HPV infection are as follows:
- Receptive anal sex.
- Having several sexual partners.
- The use of high-risk sexual practices.
- HIV infection.
- History of cervical cancer in women.
Routine HIV testing is critical in patients with anal cancer, particularly those who are at high risk.
AIN (Anal Intraepithelial Neoplasia) Treatment
If the patient is diagnosed with AIN, the doctor enrolls the patient in a surveillance program to monitor and treat the AIN and prevent it from progressing to anal cancer. Small biopsies of the afflicted area are taken at regular intervals as part of management.
The management of AIN is dependent on its severity and stages. Low-grade AIN does not need therapy because the aberrant cells clear on their own, however, high-grade AIN does need treatment. The following treatment options are considered for AIN:
- Topical therapy: This therapy includes immunomodulator creams such as imiquimod, trichloroacetic acid, and 5-fluorouracil.
- Ablative Treatments: These therapies include electrocautery, carbon dioxide laser, photodynamic therapy, and infrared coagulation.
- Surgical removal
Treatment is not required for low-grade AIN. Without any treatment, the aberrant cells return to their normal state. The doctors examine the AIN by collecting a skin sample (biopsy). They also plan regular inspections to keep an eye on the AIN.
Because the aberrant cells in high-grade AIN are less likely to heal on their own, therapy is required. Some of the skin around the anus is removed during surgery. The other medications which are required in this case are skin ointment and laser ablation.
Currently, the CDC recommends that both high-risk and average-risk groups be immunized against HPV infection with quadrivalent or nonavalent vaccinations. Clinicians need to have a working knowledge of AIN as well as the function that vaccination against HPV plays.