HIV-positive patients, women with a history of genital neoplasia and patients under pharmacologically immunosuppression (e.g. transplanted recipients, Crohn´s disease and Lupus) are a high-risk population for anal human-papillomavirus infection and associated complications, like anal precancerous lesions and anal squamous cell carcinoma. There is a lack of information on the prevalence of anal precancerous detected by routine colonoscopy in this population, by evaluating the squamocolumnar junction (the most susceptible area for lesions) during this procedure. Given, the increasing incidence rates of anal squamous cell carcinoma expected for the next two decades and the increase number of at-risk patients, the possible benefit of routine endoscopy in the diagnosis of anal precancerous lesions needs to be further explored.

Procedures in all patients:

1. Digital anorectal evaluation
2. Colonoscopy with retroflection and visualization of the anal squamocolumnar junction
3. After identification of this area 5% acetic acid will be applied.
4. Visualization under NBI/BLI.
5. Biopsies of all the suspected lesions of anal high-grade squamous lesions (HSIL).

Inclusion Criteria:

1. HIV-positive patients
2. Solid transplanted recipients
3. Crohn's disease patients under immunosuppression: steroids, thiopurines, biologics
4. Patients with lupus under immunosuppression
5. Women with a previous history of genital neoplasia (high-grade lesions or cancer) in the cervix, vagina or vulva.

Exclusion Criteria:

1. Previous anal/perianal cancer history
2. Previous known history of anal/perianal intraepithelial neoplasia
3. Pelvic radiation

HIV-positive patients, women with genital neoplasia (cervix, vulva and vagina), solid organ transplanted recipients, patients with inflammatory bowel disease and patients with Lupus.