[Perianal Kaposi's sarcoma. A case report and a review of the literature].

Kaposi's sarcoma is the most common cancer in men who have sex with men with AIDS. The estimated prevalence in the United States is 25% in patients with positive serology for the human immunodeficiency virus (HIV). The commitment of the gastrointestinal tract is seen in 40% of patients with Kaposi's sarcoma related to AIDS but lesions can occur anywhere in the body and evolve rapidly. We present a 33-year-old patient who kept sex with men, with epidemiological history of hepatitis B and syphilis, who consulted the service of Coloproctology for perianal ulcer. He was studied according to the protocols of sexually transmitted diseases, was diagnosed HIV and an excision biopsy of the lesion was performed. The diagnosis of perianal Kaposi's sarcoma was reached. Kaposi's sarcoma-HIV was staged, no other lesions were found and the patient started antiretrovirals with poor response to therapy. He evolved with rapid progression of the disease and died with the presumptive diagnosis of Fournier's syndrome at three months after the excision biopsy. We conclude that perianal ulcers are a relatively common pathology in the office of Coloproctology and differential diagnosis are different according to the positivity for HIV or not and the patient's sexual practices. We consider that is important to publish and spread these cases.