ASC-H of the cervix

by Adnan Karavelic, MD FRCPC
August 4, 2025

ASC-H stands for “atypical squamous cells – cannot rule out high-grade squamous intraepithelial lesion (HSIL)”. It is a term used in Pap smear results when abnormal cells are seen on the surface of the cervix. These changes raise concern for a precancerous condition, but they are not specific enough to confirm a diagnosis of high-grade squamous intraepithelial lesion (HSIL). Because HSIL is a precancerous condition that can lead to cervical cancer if left untreated, further testing is usually recommended when ASC-H is reported.

What causes ASC-H?

The most common cause of ASC-H is infection with high-risk types of human papillomavirus (HPV), a virus that infects the squamous cells lining the cervix.

Other causes of ASC-H include:

  • Inflammation (due to infection or irritation).

  • Postmenopausal changes, including thinning (atrophy) of the squamous cells.

  • Metaplasia, a process where one type of squamous cell changes into another.

  • Previous radiation therapy to the pelvic area.

  • Normal endometrial cells that may appear abnormal and be mistaken for squamous cells.

In many cases, the changes are not dangerous but can look suspicious under the microscope, which is why further testing is often required.

Does ASC-H mean I have cancer?

No. ASC-H does not mean cancer. It means that abnormal cells were seen and a precancerous condition such as HSIL could be present, but a definite diagnosis cannot be made from the Pap smear alone. Most people with ASC-H do not have cervical cancer. However, because ASC-H carries a higher risk of HSIL compared to other abnormal Pap smear results (like ASC-US), your doctor will likely recommend follow-up testing, such as:

  • Colposcopy – a procedure that allows the doctor to examine your cervix more closely using a special microscope.

  • Cervical biopsy – a small sample of tissue is removed for examination under the microscope.

Does ASC-H mean I have human papillomavirus (HPV)?

Not necessarily. While HPV infection is the most common cause of ASC-H, not all cases are due to HPV.

Other non-HPV causes include:

  • Postmenopausal atrophy.

  • Squamous metaplasia (a normal but reactive change).

  • Inflammation or infection.

  • Sampling of endometrial cells (especially in postmenopausal women).

Your doctor may order HPV testing alongside your Pap smear. A positive result for high-risk HPV increases the likelihood that a precancerous lesion is present.

What does ASC-H look like under the microscope?

When a pathologist examines the sample from your Pap smear under the microscope, they may see abnormal squamous cells that raise concern for HSIL but do not meet all the criteria needed to confirm the diagnosis.

These abnormal cells:

  • Are larger and darker than normal squamous cells (this is called hyperchromasia).

  • Have irregular shapes and sizes, especially in the nucleus (the part of the cell that holds DNA).

  • May be found as single cells or in small groups.

  • May show less mature cytoplasm, meaning the body of the cell is smaller or more immature-looking than expected.

Because these features are suspicious but not definitive for HSIL, the result is reported as ASC-H.

What should happen next?

If you receive an ASC-H result on your Pap smear, your doctor will likely recommend a colposcopy and possibly a biopsy to take a closer look at your cervix and confirm whether a high-grade lesion is present. Treatment will depend on whether a precancerous condition is found. If no high-grade lesion is found, your doctor may recommend close follow-up with repeat testing.

Questions to ask your doctor

  • What does ASC-H mean for me and how concerned should I be?

  • Will I need a colposcopy or biopsy to find out more?

  • Do I have high-risk HPV, and how does that affect my risk?

  • How often should I have follow-up Pap smears or HPV tests?

  • What are the treatment options if HSIL or another precancerous condition is found?

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