An abnormal finding on a Papanicolaou test in which squamous cells from the endocervix have enlarged nuclei with irregular nuclear membranes and hyperchromasia. These pathological changes are more prominent than those that are typically seen with inflammation alone. ASC-US is often associated with infection of the cervix with human papillomavirus, a virus that is associated with most cases of cervical cancer. In some cases the abnormality resolves on its own; in others, it is associated with higher-grade lesions of the uterine cervix.