A finding of abnormal cells in the tissue that lines the outer part of the cervix. ASCUS is the most common abnormal finding in a Pap test. It may be a sign of infection with certain types of human papillomavirus (HPV). It may also be a sign of a benign (not cancer) growth, such as a cyst or polyp or, in menopausal women, of low hormone levels. More testing, such as an HPV test, may be needed. Also called ASC-US and atypical squamous cells of undetermined significance.