Liquid-based Anal Cytology as a Screening Tool for Prevention of Anal Cancer in at-risk Populations: A Single-Center Retrospective Analysis on 111 Patients

Abstract

Objective Squamous cell carcinoma of the anus (SCCA) is associated with human papillomavirus (HPV) infection in almost 90% of the cases. Its incidence is alarmingly high among men who have sex with men (MSM) and continues to increase at an average rate of 2% per year. The objective of the present study is to evaluate the usefulness and performance of liquid-based anal cytology as a screening tool for prevention and early detection of SCCA in a cohort of at-risk men. Method We conducted a retrospective study including 111 MSM, aged between 22 and 62 years old, who underwent anal cytological screening with a liquid-based Pap test at our sexually transmitted diseases (STDs) clinic from January 2015 to March 2017. Results Out of 111 anal smears, 57 (51,4%) resulted negative, 42 (37,8%) abnormal, and 12 (10,8%) unsatisfactory for the cytological evaluation. Only patients with an abnormal cytology underwent anoscopy and subsequent biopsy. The histological results were as follows: negative for squamous intraepithelial lesion (SIL) in 5 cases, low-grade SIL (L-SIL) in 21, high-grade SIL (H-SIL) in 5, SCCA in 1. Five patients had a normal anoscopy and biopsy was not taken. Conclusion Liquid-based cytology, reducing the “darkening factors” typical for the conventional smears, has a higher positive predictive value than the traditional technique. Moreover, a cytological diagnosis of atypical squamous cells of undetermined significance (ASC-US) or L-SIL may hide a severe dysplasia or even a carcinoma. Thus, all patients with an abnormal anal cytology at any grade should be considered for anoscopy.

Comprehensive Review of Anal Cytology

“…However, unlike cervical cancer, guidelines for anal cancer screening, including whom to screen, are not yet well defined and/or standardized [3-5, 11, 12]. Still, recommendations from multiple societies and institutions do exist and often include similar modalities for screening and work-up, such as digital anorectal exam (DARE), anoscopy, both standard and highresolution (HRA), HPV testing, and anal cytology, with anal cytology as a mainstay of many proposed guidelines, especially for high-risk populations [4,5,9,[12][13][14][15][16][17][18][19][20].…”

“…Five percent acetic acid and/or Lugol's solution can be used to highlight suspicious areas for targeting biopsy [9]. Many guidelines suggest utilizing anal cytology first, then following up with HRA if any abnormalities are detected [9,11,16,17]. Nonetheless, multiple studies have looked at the performance of screening modalities alone and in combination up front, with varying results.…”