What Causes Cervical Cysts and When to See a Doctor

Cervical cysts form when glands in the cervix become blocked, trapping mucus or other fluid beneath the surface tissue. The overwhelming majority are nabothian cysts, which develop when the squamous cells that line the outer cervix grow over and seal off the tiny mucus-producing glands underneath. These cysts are so common in women of reproductive age that most are discovered by accident during a routine pelvic exam or ultrasound and never cause a single symptom. Still, not every cervical cyst is a simple nabothian cyst, and understanding the less common types helps explain why doctors sometimes want a closer look.

Nabothian Cysts and Why They Are So Common

Nabothian cysts are the most frequently encountered cystic lesions of the cervix. They form through a process called squamous metaplasia: the squamous epithelium that covers the outer cervix gradually spreads inward and grows over the openings of endocervical glands. Once those gland openings are sealed, mucus has nowhere to go and collects into small, fluid-filled pockets within the cervical tissue.¹ This process is a normal part of how cervical tissue renews itself, which is why nabothian cysts are not considered a disease. They are closer to a byproduct of routine tissue turnover.

Several things speed up or trigger that gland-blocking process. Childbirth is the most commonly cited cause, because the physical trauma of delivery can damage the cervical surface and set off a round of tissue repair that buries gland openings. Minor trauma from procedures like cervical biopsies and chronic cervical inflammation (cervicitis) also play a role.² Infections and long-standing irritation keep the cervical lining in a cycle of damage and repair, making it more likely that new squamous tissue will grow over a gland before it has a chance to drain.

Most nabothian cysts measure between 2 and 10 millimeters across, roughly the size of a peppercorn to a small pea. At that size they are painless and invisible to the person who has them. Giant nabothian cysts, defined as those exceeding about 4 centimeters, do exist but are rare. When they grow that large, they can press on surrounding structures and start to produce symptoms like pelvic pressure, difficulty emptying the bladder, or irregular bleeding.²

Less Common Types of Cervical Cysts

While nabothian cysts account for most cervical cysts, several other types appear on the spectrum of cystic cervical lesions. Understanding them matters mainly because some can look alarming on imaging or during a physical exam, even though they are usually benign.

Tunnel Clusters

Tunnel clusters are benign groupings of endocervical glands that sit near the surface of the cervix. They come in two forms. Type A clusters are tightly packed nests of small tubules that look almost solid. Type B clusters are distended, mucus-filled cysts that can grow large enough to be visible on imaging and even during a speculum exam.³ The clinical importance of Type B tunnel clusters is that they can look strikingly similar to a rare form of cervical cancer called adenoma malignum (minimal-deviation adenocarcinoma). Because of this visual resemblance, a biopsy is sometimes needed to confirm that the lesion is harmless. Tunnel clusters tend to show up in women over 40 who have had multiple pregnancies, though they can appear at other ages.

Lobular Endocervical Glandular Hyperplasia (LEGH)

LEGH is a benign overgrowth of endocervical glands that can produce a distinctive cluster of small and large cysts deeper in the cervical tissue. On MRI, the pattern of a central solid or microcystic area surrounded by larger peripheral cysts has been described as a “cosmos pattern.”¹ LEGH tends to sit higher in the cervix, closer to the point where the cervix meets the uterine body. It gets attention from pathologists because some research has explored whether it could be a precursor to adenoma malignum, though most cases are considered harmless on their own.

Gartner Duct Cysts

Gartner duct cysts are an entirely different animal. They arise not from cervical glands but from embryonic tissue remnants. During fetal development, structures called the mesonephric (Wolffian) ducts normally disappear in female embryos. When small segments persist into adulthood, they can form fluid-filled cysts along the vaginal wall or the lateral aspect of the cervix.⁴ These cysts are rarely seen and are typically discovered incidentally. They can occasionally enlarge during pregnancy due to hormonal changes and, in extreme cases, present as a prolapsing mass.

Cervical Endometriosis as a Cystic Lesion

Endometriosis is usually associated with the pelvic cavity and ovaries, but it can also involve the cervix. Cervical endometriosis means that tissue resembling the uterine lining has established itself on or within the cervix. When that tissue responds to the menstrual cycle, it can bleed internally and form cystic pockets of old blood. The condition ranges from completely silent to causing heavy or erratic bleeding and chronic pelvic pain.⁵

There are two recognized forms. Primary cervical endometriosis stays on the surface of the cervix and does not extend deep into the tissue. Secondary cervical endometriosis, which is more common, represents extension from disease elsewhere in the pelvis, often from the area behind the cervix and in front of the rectum.⁵ A somewhat surprising finding is that cervical surgery itself can trigger endometriosis at the surgical site. In one study of women who had undergone cone biopsies, over 40 percent developed endometriosis or related tissue changes at the healed biopsy location, sometimes appearing as early as two months after the procedure.⁶ The changes appeared to result from the healing tissue differentiating abnormally after the surgical injury.

When Cervical Cysts Are Usually Harmless

For the vast majority of women, a cervical cyst discovered during a routine exam or imaging study requires nothing more than a note in the medical chart. Small nabothian cysts are considered a normal finding. They do not raise the risk of cervical cancer, they do not interfere with Pap smear results in any meaningful way, and they do not need to be drained or removed.⁷ If your provider mentions a nabothian cyst in passing, the appropriate level of concern is essentially zero.

The same generally applies to tunnel clusters, LEGH, and small Gartner duct cysts, though these rarer types may prompt a follow-up ultrasound or MRI simply because they are less familiar to clinicians and can look unusual on initial examination. The reassurance, however, is that these are all benign entities.

When to See a Doctor

Even though cervical cysts are overwhelmingly benign, certain signs should prompt a visit to your healthcare provider. The concern is less about the cyst itself and more about making sure what looks like a cyst is not actually something else.

New or unusual bleeding: Bleeding between periods, bleeding after intercourse, or postmenopausal bleeding can have many causes, but cervical lesions of any kind are one reason to investigate. A growing cystic mass in the cervix occasionally mimics a cervical malignancy on exam.
Watery vaginal discharge: A persistent, watery discharge is one of the features clinicians use to distinguish deep nabothian cysts from minimal-deviation adenocarcinoma. The absence of watery discharge tends to point toward a benign cyst, while its presence warrants further workup.⁸
Pelvic pain or pressure: Small cysts do not cause pain. If you experience a sensation of fullness, pressure, or aching in the pelvis along with a known cervical cyst, the cyst may have grown large enough to affect nearby organs, or it may not be a simple cyst at all.
Difficulty urinating or having bowel movements: A very large cervical cyst can press on the bladder or rectum. This is uncommon but has been documented with giant nabothian cysts.
A rapidly growing or changing mass: If imaging shows that a previously stable cyst has grown significantly, or if new cysts keep appearing, further evaluation is warranted to rule out a glandular abnormality.

None of these symptoms mean you have cancer. They mean the picture is no longer clearly benign and deserves a closer look.

How Cervical Cysts Are Evaluated

When a cervical cyst needs more than a brief mention, the evaluation typically proceeds in steps. A standard pelvic ultrasound can show the cyst’s size, shape, and location. For cysts that are deep in the cervical wall, multiple, or have an unusual appearance, MRI provides much more detail. On MRI, a simple nabothian cyst appears as a round or oval fluid-filled pocket that does not light up after contrast dye is injected. That non-enhancing behavior is a strong indicator of a benign cyst.⁸

By contrast, a malignant lesion like adenoma malignum tends to show enhancement after contrast injection and may have irregular borders or solid components mixed in with the cystic areas. The challenge is that some benign conditions, like Type B tunnel clusters and LEGH, can also look complex on imaging. This overlap is the main reason biopsies are sometimes performed even when the clinical suspicion for malignancy is low.⁹ The goal is not to alarm you but to be thorough, because distinguishing these benign mimics from the rare malignant look-alike requires tissue confirmation.

Treatment Options

Most cervical cysts require no treatment at all. A small nabothian cyst is left alone and may even resolve on its own as the cervical tissue continues to remodel over time. Your doctor may recommend periodic imaging to track size if a cyst is on the larger side, but watchful waiting is the norm.

When treatment is needed, the approach depends on why. A giant nabothian cyst causing symptoms like urinary difficulty or pain can be drained or surgically excised. Drainage alone sometimes leads to the cyst refilling, so excision is generally preferred for cysts that are large enough to be symptomatic. For endometriosis-related cystic lesions of the cervix, treatment follows the broader principles of endometriosis management, which may include hormonal therapy to suppress the menstrual cycle’s effect on the tissue or surgical removal of the endometriotic implants.

Tunnel clusters and LEGH that are confirmed as benign on biopsy typically do not need any further intervention. The diagnosis itself is the treatment, in the sense that once malignancy has been excluded, the clinical issue is resolved. Your provider may recommend a follow-up imaging study six to twelve months later to confirm stability, after which no further monitoring is usually needed.

Can Cervical Cysts Affect Fertility?

This is a question many women ask, and the honest answer is: almost never. The cervical canal through which sperm must travel is a separate passageway from the glands where nabothian cysts form. A few small cysts sitting in the cervical wall do not block that channel or change the quality of cervical mucus in a meaningful way.

The exceptions are rare and involve very large or very numerous cysts. Giant nabothian cysts can theoretically distort the cervical anatomy enough to interfere with sperm transport or make it harder for a fertilized egg to implant, though documented cases linking giant cysts directly to infertility are uncommon. One published case described a woman with primary infertility who had giant nabothian cysts, but establishing a direct causal connection is difficult because infertility is multifactorial.² If you are undergoing a fertility workup and cervical cysts are found, your reproductive specialist can assess whether they are likely contributing to the problem or are incidental bystanders.

The Adenoma Malignum Question

One reason cervical cysts sometimes generate more anxiety than they deserve is the existence of adenoma malignum, a rare and deceptive form of cervical adenocarcinoma. This cancer looks benign even under the microscope, earning its name (“malignant adenoma”) from its ability to fool pathologists. On imaging, it can present as multiple cystic spaces in the cervix, which is why it enters the conversation when doctors see multi-cystic cervical lesions.⁸

Adenoma malignum is genuinely rare. The incidence of cervical adenocarcinoma overall has been rising, but adenoma malignum remains a small fraction of those cases.⁸ The reason clinicians keep it in mind is not because it is common but because missing it has serious consequences. The distinguishing features on MRI include enhancement of the cyst walls after contrast injection and the presence of solid tissue components. A watery vaginal discharge is another clinical clue. If neither of those features is present and the cysts look smooth, round, and fluid-filled, the odds strongly favor a benign diagnosis.

Understanding that this rare entity exists can actually be reassuring rather than frightening. It explains why your doctor might order an MRI or suggest a biopsy for cervical cysts that look unusual. The investigation is not a sign that your doctor suspects cancer; it is a sign that they are being careful to exclude the one uncommon mimic that matters.

Cervical Cysts After Surgical Procedures

Women who have had procedures on the cervix, such as a cone biopsy to evaluate or treat precancerous cells, sometimes develop new cystic lesions at the surgical site. The healing process involves new tissue growing over the raw area left by the surgery, and that tissue can trap glands in the same way squamous metaplasia traps them in ordinary nabothian cyst formation. The result can be nabothian-like cysts at the scar, or in some cases, endometriosis or related tissue changes at the biopsy site.

In the cone biopsy study mentioned earlier, abnormal glandular tissue appeared at the healed site in roughly two out of three post-surgical cervices examined, with endometriosis specifically found in about 43 percent of cases. The changes could appear anywhere from two months to over seven years after the procedure.⁶ These post-surgical changes are not dangerous in themselves, but they are worth knowing about because they can cause confusion on follow-up exams. A cyst or unusual-looking tissue at a previous cone biopsy site does not mean the precancerous condition has returned. It may simply be a byproduct of healing.

If you have had a cervical procedure and your provider notes a new cyst or tissue change at the site, mentioning your surgical history helps them interpret the finding correctly. Knowing that post-procedure cystic changes are common can spare you an unnecessary round of worry while your doctor confirms the diagnosis.

1
Journal of Magnetic Resonance Imaging. Various cystic lesions in uterine cervix: MR Imaging-Anatomic-Histopathologic correlation
2
PubMed Central. Cervical giant Nabothian cysts in a woman with primary infertility: a case report
3
PubMed Central. “Tunnel Clusters” an Unexplored World for Gynaecologists: A Case Report
4
PubMed Central. Gartner duct cyst in pregnancy presenting as a prolapsing pelvic mass
5
PubMed. A Rare Case of the Cervical Endometriosis and Overview of the Literature
6
PubMed. Cone biopsy causes cervical endometriosis and tubo-endometrioid metaplasia
7
Journal of Wasit for Science and Medicine. Histological manifestations of the Cervix with Chronic Cystic Cervicitis and Nabothian Cyst: Case Report
8
PubMed. MRI of endocervical glandular disorders: three cases of a deep nabothian cyst and three cases of a minimal-deviation adenocarcinoma
9
PubMed. Multilocular cystic lesions in the uterine cervix: broad spectrum of imaging features and pathologic correlation