Multi-institutional 10-year retrospective review of amoeba diagnosed on cytologic evaluation of anal pap tests: what is the significance?

Intestinal amoebae are usually transmitted via ingestion of amoebic cysts in fecally contaminated water or food. However, other modes of transmission include sexual contact through anal-oral sex. While the primary role of anal cytology is the detection of anal cancer and precursor lesions, organisms can also be identified. Despite this, assessment of the clinical significance of cytologic identification of amoebae is lacking in the literature. A 10-year retrospective review of the pathology archives of 2 institutions in Boston, Massachusetts was conducted. Anal Pap tests that identified amoeba were reviewed and correlated with the medical records for investigation into clinical parameters and patient management. A total of 46 cases were identified between the 2 sites. The majority of patients were male (95.7%) and endorsed having sex with men (84.8%). Only a minority endorsed recent travel (6.5%). Most of the patients were also HIV (human immunodeficiency virus)-positive (71.1%) with all of these patients being well-controlled on antiretroviral therapy. Most patients were asymptomatic (87.0%). On review of the anal Pap tests, the average organism number per case was 35.4. In the majority of cases, follow-up microbiology testing for confirmation and/or speciation was not performed (89.1%) and were not treated (93.5%). While identification of amoeba is possible on anal cytology, the clinical significance remains unclear as most patients were asymptomatic and not treated in this series. Ultimately, the clinical setting likely plays an important role in determination of management. •Anal Pap tests are integral in the surveillance for cancer in high-risk populations such as men who have sex with men (MSM). While this is the main use of anal Pap tests, various infections including intestinal amoeba can be identified. Despite this, there is a paucity of literature regarding the detection of amoeba on anal Pap tests.•In this 10-year, multi-institutional retrospective study, we describe the experience of 2 large academic medical centers with the detection of amoeba on anal Pap tests with investigation into the clinical significance of this finding.•A total of 46 cases were identified between the 2 sites. The vast majority were from MSM (94.8%) without recent history of travel. The majority of patients were asymptomatic (87.0%).•On follow-up, the majority of cases were not further characterized by microbiology studies (89.1%) and the vast majority of patients were n