ASC-H of the Cervix: Understanding Your Pathology Report

by Adnan Karavelic, MD FRCPC
May 14, 2026

ASC-H stands for “atypical squamous cells — cannot rule out high-grade squamous intraepithelial lesion (HSIL).” It is a result on a Pap test (also called a Pap smear) that means abnormal squamous cells were found in the sample from your cervix, and these cells raise enough concern that a precancerous condition called high-grade squamous intraepithelial lesion (HSIL) might be present.

ASC-H is not a diagnosis of cancer. It is an uncertain finding, meaning the cells look too abnormal to be dismissed but not abnormal enough to warrant a definite diagnosis based on the Pap test alone. Because HSIL can progress to cervical cancer if not treated, an ASC-H result is taken seriously and almost always leads to a follow-up procedure to look more closely at your cervix. This article will help you understand what ASC-H means, why it happens, and what the next steps in your care are likely to be.

What causes ASC-H?

The most common and clinically significant cause of ASC-H is infection with high-risk human papillomavirus (HPV) types. High-risk HPV types — particularly HPV16 and HPV18 — can cause changes in the squamous cells lining the cervix that raise concern for HSIL. However, not every ASC-H result is caused by HPV. Several other conditions can produce cells that look abnormal enough to be reported as ASC-H without representing a precancerous process:

HPV infection — The most common cause. High-risk HPV types can alter the appearance of squamous cells in ways that suggest a precancerous change. A positive HPV test alongside an ASC-H result increases the likelihood that a precancerous lesion is present.
Postmenopausal atrophy — After menopause, the cells lining the cervix become thinner and less mature due to lower estrogen levels. These atrophic cells can sometimes appear abnormal, resembling HSIL.
Squamous metaplasia — A normal process in which one type of squamous cell gradually replaces another in the transformation zone. Immature metaplastic cells can occasionally have features that raise concern for HSIL.
Inflammation or irritation — Infections, an intrauterine device (IUD), or other sources of irritation can cause reactive changes in squamous cells that mimic more serious findings.
Prior radiation therapy — Radiation to the pelvic area can cause long-lasting changes in cervical cells that may appear abnormal on a Pap test.
Endometrial cells — Cells from the lining of the uterus (the endometrium) can occasionally be sampled on a Pap test. In some cases, these cells are mistaken for abnormal squamous cells, particularly in postmenopausal people.

In many cases, the underlying cause of an ASC-H result cannot be determined from the Pap test itself — which is why further testing is recommended.

What does ASC-H look like under the microscope?

When a pathologist or a specially trained cytotechnologist examines the Pap test sample under the microscope, the cells in an ASC-H result show features that raise concern for HSIL but do not fully meet all the criteria needed to confirm that diagnosis. Normal squamous cells have a relatively large amount of cytoplasm (the body of the cell) surrounding a small, evenly shaped nucleus (the part of the cell that holds the genetic material). In ASC-H, these proportions are altered:

Enlarged, dark nuclei — The nuclei in ASC-H cells are larger and darker than those of normal squamous cells. Abnormal darkening of the nucleus is called hyperchromasia.
Irregular nuclear shape — The nuclei may have uneven or irregular outlines rather than the smooth, rounded shape seen in healthy cells.
Reduced cytoplasm — The cells have less cytoplasm relative to the size of the nucleus. This increased nuclear-to-cytoplasmic ratio is a hallmark of a cell behaving abnormally.
Immature-appearing cell bodies — The cytoplasm of the abnormal cells may look dense or immature, similar to the appearance of cells that have not completed their normal development.
Isolated cells or small groups — The abnormal cells are often found singly or in small clusters rather than in large sheets, which makes them harder to evaluate.

These features are suspicious for HSIL but are not specific enough on their own to make a definitive diagnosis, which is exactly what the term “cannot rule out HSIL” is intended to convey.

How is ASC-H different from ASC-US?

ASC-US (atypical squamous cells of undetermined significance) is a related Pap test result, but it carries less concern than ASC-H. In ASC-US, the abnormal cells are only mildly atypical and are associated primarily with a low-grade squamous intraepithelial lesion (LSIL). Many ASC-US results resolve on their own, particularly when HPV testing is negative, and management in some cases involves repeat Pap testing rather than immediate colposcopy.

ASC-H, by contrast, specifically raises concern for high-grade disease. The abnormal cells in ASC-H look more like the cells seen in HSIL — a precancerous condition with a meaningful risk of progressing to cervical cancer. Because of this heightened concern, colposcopy is recommended for almost all ASC-H results, regardless of HPV test status, and the risk of finding HSIL on biopsy is substantially higher after ASC-H than after ASC-US.

What happens after an ASC-H result?

Colposcopy is the standard next step for almost all ASC-H results. During a colposcopy, the doctor uses a colposcope — a special magnifying instrument — to examine the surface of the cervix in detail. Areas that look abnormal are identified, and a small tissue sample called a biopsy is taken from those areas and sent to the laboratory. A second sample may also be collected from inside the cervical canal using a procedure called endocervical curettage, particularly if the area of concern extends inside the canal, where it cannot be fully seen with the colposcope. Colposcopy alone does not confirm or exclude HSIL — the biopsy provides a definitive answer.

Several outcomes are possible after the biopsy:

Biopsy shows HSIL (CIN2 or CIN3) — A precancerous lesion is confirmed. Treatment is recommended to remove the abnormal area, usually with a loop electrosurgical excision procedure (LEEP) or a cone biopsy. The goal is to remove precancerous cells before they can progress to cancer.
Biopsy shows LSIL or CIN1 — A lower-grade precancerous change is found. This often resolves on its own and is typically managed with close monitoring rather than immediate treatment.
Biopsy is normal — No precancerous lesion is found. Even so, close follow-up with repeat Pap and HPV testing is recommended because the ASC-H result indicates a meaningfully increased risk, and a small lesion may have been missed at the time of colposcopy.
Biopsy shows invasive cancer — Although uncommon, an ASC-H result can sometimes reveal invasive cervical cancer on biopsy. In this case, you will be referred to a gynecologic oncologist for staging and treatment planning.

An HPV test, if performed, also helps shape the follow-up plan. A positive high-risk HPV test alongside ASC-H confirms a viral cause and supports proceeding to colposcopy. A negative HPV test in the setting of ASC-H does not eliminate the concern: colposcopy is still recommended because a small but meaningful proportion of ASC-H results with negative HPV testing still turn out to show HSIL on biopsy. Your doctor or gynecologic specialist will guide the timing and type of follow-up based on your biopsy result, HPV status, age, and overall medical history.

Questions to ask your doctor

What does ASC-H mean for me, and how worried should I be about this result?
Will I need a colposcopy, and how soon should it be scheduled?
Will a biopsy be taken during my colposcopy, and from where?
Was an HPV test also performed, and how does the result affect my next steps?
What is the chance that my biopsy will show HSIL or a more serious finding?
If HSIL is found, what are my treatment options and how effective are they?
What is the difference between ASC-H and ASC-US, and which one do I have?
How will I be monitored after colposcopy and biopsy, and for how long?
If my biopsy is normal, what is the recommended follow-up schedule?
Are there any symptoms I should watch for between appointments?
Could postmenopausal changes or another non-HPV cause be responsible for my ASC-H result?
Should I consider HPV vaccination if I have not already been vaccinated?