Cytology in Anal Cancer Screening: Practical Review for Clinicians

Abstract

The incidence and mortality of anal squamous cell carcinoma (SCC) are expected to continue to increase in the next 20 years. High-risk groups for anal SCC, i.e., human immunodeficiency virus (HIV)-positive patients, men who have sex with men (MSM), women with previous genital neoplasia, and solid-organ transplant recipients, have been identified. HIV-positive MSM have the highest risk, and some societies have advocated for anal cancer screening to be done in this population. Screening for anal SCC follows the same principles as that for cervical cancer since there are similarities between the two types of cancers. Anal cytology has been recommended as an initial screening method for high-risk groups, e.g., HIV-positive MSM. Normally, the cytology is liquid based and collected blindly by a clinician using a Dacron swab and it is especially used for internal lesions detection. The sensitivity to predict anal high-grade squamous intraepithelial lesions is higher in immunosuppressed patients with a high burden of the disease. The report should include the classification, normally according to the Bethesda terminology and the sample adequacy, in a manner similar to that for cervical cytology. In cases involving unsatisfactory samples, it is important to repeat the procedure given the prevalence of anal squamous cytological abnormalities in follow-up cytology procedures. The absence of transformation zone cells in anal cytology seems to increase the risk of false-negative results.

Recommendations Favoring Anal Cytology as a Method for Anal Cancer Screening: A Systematic Review

“…Anal cytology is routinely performed as a liquid-based cytology, using a Dacron swab and, in contrast with the procedure for the cervix, collected blindly [28]. The recommended unsatisfactory sample rate in high-risk groups (e.g., HIV-positive MSM) should be <5% [29].…”

“…The recommended unsatisfactory sample rate in high-risk groups (e.g., HIV-positive MSM) should be <5% [29]. The Bethesda terminology is normally used for classification, as it is for the cervix [28]. A proper digital anorectal examination should always be performed to detect masses suggesting anal cancer that may be missed by cytology or by HRA [17].…”

Human papillomavirus‐related cancer risk for solid organ transplant recipients during adult life and early prevention strategies during childhood and adolescence

“…Among these two cancer types, HPV types 16 and 18 account for 87% of anal cancers and 84.9% of oropharyngeal cancers 57 . There is currently no standard screening for HPV‐related anal or oropharyngeal cancers, at least not in the pediatric age group, although anal cytology has been proposed and its utility is currently being evaluated for adults who are high risk for HPV‐associated malignancies, including SOT recipients 58 . The lack of screening further emphasizes the need for primary prevention strategies of HPV vaccination and behavioral counseling in reducing HPV‐related cancers.…”

“…23 Specifically, recent studies have demonstrated a true reduction in abnormal cervical cytology, cervical precancers, cervical cancers, and anal cancers with the use of HPV vaccine, [24][25][26] as well as early evidence of possible oropharyngeal cancer prevention. 27 There are currently three types of vaccines available: the quadrivalent (HPV types 6,11,16,18), licensed in 2006 for women and in 2009 for men; the bivalent (HPV types 16 & 18), licensed for women in 2009; in the United States, currently only the 9-valent (HPV types 6,11,16,18,31,33,45,52,58) is available and was approved for both women and men in 2014. 28…”

Proteases and HPV-Induced Carcinogenesis

“…Anal cancer screening is not a consensus among international societies [216]. Intraepithelial lesions are rare in the general population, which would not justify a universal screening program; however, screening for precancerous lesions in the higher-risk population should be considered, e.g., for HIV-positive, MSM, and immunocompromised patients, and women with a history of dysplasia or invasive cervical carcinoma [216][217][218][219][220].…”