EBV-associated anorectal lymphomas in patients with acquired immune deficiency syndrome

Primary lymphomas of the gastrointestinal tract represent 9% of all non-Hodgkin lymphomas, and of these only 3% arise in the rectum or anus. In contrast to their rare occurrence in the general population, the incidence of anorectal lymphomas in patients with acquired immune deficiency syndrome (AIDS), particularly homosexual patients, may be as high as 26% as reported in our own series of AIDS-associated lymphomas. To determine the characteristics of this entity, we studied 15 cases of primary anorectal lymphoma in AIDS patients and compared them with four cases of anorectal lymphoma unrelated to AIDS. The cases in our study were also compared with the reports of rectal lymphoma in the medical literature over the past 30 years. In the present series, the AIDS patients were all male with a median age of 34 years, human immunodeficiency virus (HIV)-positive, with homosexuality as the main risk factor. The four non-AIDS patients included a woman and had a median age of 66.5 years. Histologically, the anorectal lymphomas in AIDS patients were all high grade, predominantly immunoblastic, and polymorphous. In the non-AIDS patients, only two of four lymphomas were high grade, including one Burkitt type. All tumors were of B-cell phenotype. In the AIDS-associated anorectal lymphomas, the presence of Epstein-Barr virus (EBV) in a latent form was demonstrated by an abundance of Epstein-Barr-encoded RNA (EBER) in 14 of 15 cases and latent membrane protein (LMP) in four cases. All anorectal lymphomas unrelated to AIDS were negative for EBV. The unusual anorectal location of AIDS-associated lymphomas is explainable by the high incidence of preceding traumatic lesions and chronic infections in the area. As a result, EBV-carrying B cells may be attracted to the field providing the cell population that, under the conditions of immune deficiency, is able to give rise to high-grade lymphomas.