From the Guidelines
ASCUS cells, or Atypical Squamous Cells of Undetermined Significance, are abnormal cells found in Pap smear results that don't clearly indicate whether they are benign or potentially precancerous, with a prevalence of approximately 4 percent of cytologic smears, as reported by 1. These cells show minor changes in size, shape, or other characteristics that make them different from normal squamous cells that line the cervix, but the changes aren't severe enough to definitively diagnose as precancerous.
- The risk of CIN 2 or more serious abnormality in women with ASCUS is 9.7 percent, as stated in 1.
- Reflex HPV DNA testing is the preferred triage option for non-adolescent women with ASCUS, with colposcopic evaluation for women who are HPV positive, as recommended by 1.
- The management of ASCUS cytology tests allows for the use of HPV testing to stratify the risk for the development of cervical cancer precursor lesions, as discussed in 1. Some key points to consider in the management of ASCUS include:
- The inter- and intra-observer reproducibility of an ASC-US interpretation is less than that for the reliable, unequivocal diagnostic categories of LSIL and high-grade squamous intraepithelial lesion (HSIL), as noted in 1.
- The risk of precancerous lesions following an HPV-negative, ASC-US cytology result is very low, and not different from a negative cotest, as reported in 1. Therefore, continued routine screening is recommended for women with HPV-negative, ASC-US cytology results, with a 3-year interval for cytology screening of women ages 21–29 or 30–65 years old, and a 5-year interval for cotesting of women ages 30–65 years old, as recommended by 1.
From the Research
Definition of ASCUS Cells
- ASCUS stands for Atypical Squamous Cells of Undetermined Significance, which is a category of cervical cytologic findings that are suggestive but not definitive of squamous intraepithelial lesions 2, 3, 4, 5, 6.
- ASCUS accounts for 5-10% of reported Papanicolaou (Pap) smears 4.
- The management of women with ASCUS cytologic findings remains controversial 2, 4.
Prevalence of ASCUS Cells
- The frequency of initial abnormal cytology was 65% for ASCUS, 27% for low-grade squamous intraepithelial lesion (LSIL), and 3.4% for ASC cannot exclude high-grade intraepithelial lesion (ASC-H) 3.
- Of 29,827 patients who had a Pap smear, ASCUS were detected in 1387 (5%) and persisted in the repeat smear of 225 (16%) 2.
- The ratio of ASCUS to low-grade squamous intraepithelial lesion (LGSIL), high-grade squamous cell intraepithelial lesion (HGSIL) or squamous cell carcinoma (SCC) was 5/34,1/34, and 0/34, respectively 4.
Management of ASCUS Cells
- Colposcopic evaluation after a repeated Pap smear with ASCUS is an appropriate cost-effective management 2.
- Routine cytological follow-up may be an appropriate method in the management of ASCUS instead of immediate colposcopy 3.
- Cytologic follow-up of women with low-grade Pap smear abnormalities will identify a large number whose smears will regress to normal 5.
- A small but significant proportion of women showed subsequent high-grade squamous intraepithelial lesion (HSIL) 5.
- Detection of carcinogenic HPV DNA using the Hybrid Capture tube-based (HCT) test was almost as sensitive for detecting CIN 2/3 as a solitary repeat Pap smear using an ASCUS or more severe positive threshold 6.