Anal Cytology: Institutional Statistics, Correlation With Histology, and Development of Multidisciplinary Screening Program With Review of the Current Literature

Abstract

Context.— The incidence of anal cancer in the United States is on the rise in high-risk populations. The anal Papanicolaou test (APT) is advocated as a screening tool, in addition to digital rectal examination and high-resolution anoscopy. Objective.— To review our experience and the current literature to create, in cooperation with clinicians, a standardized screening and treatment algorithm given our large volume of APTs. Data Sources.— All APTs collected between January 2013 and June 2015 were reviewed and correlated with follow-up/concurrent biopsy diagnoses, and clinical and social history. In total, 1417 APTs were performed on 1185 patients and APT results were as follows: 17.4% (247 of 1417) unsatisfactory; 27.9% (395 of 1417) negative; 19.5% (276 of 1417) atypical squamous cells of undetermined significance (ASC-US); 24.1% (342 of 1417) low-grade squamous intraepithelial lesion (LSIL); 3.6% (51 of 1417) atypical squamous cells, cannot exclude high-grade squamous intraepithelial lesion (HSIL) (ASC-H); and 7.5% (106 of 1417) HSIL. In total 376 cases (26.5%) had concurrent/follow-up biopsy. Review of all unsatisfactory cases with squamous intraepithelial lesion (SIL) on biopsy showed LSIL in 19.2% (5 of 26). Anal Papanicolaou test with cytologic abnormality (ASC-US+) had an 83.8% (315 of 376) rate of biopsy-proven disease, and sensitivity was higher (92%) for high-grade anal intraepithelial neoplasia or worse (AIN2+). Overall detection of AIN2+ using ASC-US+ showed specificity of 26%, negative predictive value of 92%, and positive predictive value of 26%. Conclusions.— Anal cytology has a high abnormal rate (54.7%) and sensitivity but poor correlation with histologic grade. High unsatisfactory rate indicates need for improvement in sampling with 68.4% of cases having SIL on biopsy. Multidisciplinary effort led to improvements in sampling, cytologic interpretation, and development of a standardized management algorithm.