While Pap smears are very helpful in finding cervical cancer and its' precursers, not all cases of invasive cancer of the cervix will be detected by Pap smears. Pap smears have a known false negative rate, and some cancers may be highly aggressive in their ability to invade underlying stromal cells, but not particularly exfoliative. The "Barrel Lesion" of the cervix is one example of such a lesion.

For this reason, any visible lesion of the cervix should be biopsied to identify those with cancer. Not included in this need for biopsy would be such common and benign cervical lesions as cervicitis, cervical ectropion, and nabothian cysts.