Mucinous Cystadenofibroma of the Ovary: Understanding Your Pathology Report

Section Editor: Kianoosh Keyhanian MD FRCPC
August 29, 2026

A mucinous cystadenofibroma is a noncancerous (benign) type of ovarian tumor. It consists of fluid-filled spaces called cysts, along with firm, fibrous supporting tissue. The cysts are lined by cells that produce a thick, gelatinous, mucus-like fluid called mucin. The name describes what the pathologist sees. “Cyst” refers to the fluid-filled spaces, “adeno” to the gland-like lining cells, and “fibroma” to the fibrous tissue between them.

A mucinous cystadenofibroma is not cancer, and it does not spread to other parts of the body. It is closely related to a mucinous cystadenoma, and the two differ only in how much fibrous tissue is present. Like other mucinous ovarian tumors, it can grow very large before it is found. It is usually located in only one ovary.

This article will help you understand what this diagnosis means on your pathology report, what each term means, and why it matters for your care.

What causes a mucinous cystadenofibroma?

The cause of a mucinous cystadenofibroma is not known. This tumor is not caused by an infection, and it is not contagious. No lifestyle factor has been shown to cause it, and in most cases there is no identifiable reason why one person develops it. These tumors can occur at any age. They are found most often in adult women during the reproductive years and around the time of menopause.

Researchers have found changes in a gene called KRAS in many benign mucinous ovarian tumors. KRAS normally works like an on-off switch for the signals that tell a cell to grow and divide. A change in the gene can leave that switch stuck in the “on” position, so the cells keep growing. This change is part of how these tumors form, but your treatment team does not test for it, and it will not appear on your pathology report.

What are the symptoms?

Many mucinous cystadenofibromas cause no symptoms. Small tumors are often discovered by chance, during an imaging test or an examination performed for another reason. Because these tumors can become large, symptoms, when they occur, usually come from the size of the mass itself. They may include:

Abdominal swelling or bloating — An increase in the size of the abdomen, or a feeling of fullness. Mucinous tumors are among the largest tumors in the body, so this is a common reason to seek medical attention.
Abdominal or pelvic pain — Discomfort or pain low in the abdomen or pelvis, often described as dull or dragging.
Pressure on nearby organs — A large cyst can press on the bladder or bowel. This may change how often you need to urinate or your bowel habits.
Sudden, severe pain — A large ovarian cyst can twist on its blood supply, a problem called torsion. This causes sudden severe pain and needs urgent medical attention.

These symptoms are common and have many possible causes. None of them is specific to a mucinous cystadenofibroma. Any persistent abdominal or pelvic symptom should be evaluated by a doctor.

How is the diagnosis made?

For most women, doctors diagnose a mucinous cystadenofibroma after surgically removing the tumor and sending it to a pathologist for microscopic examination. Surgery may remove the cyst alone, the whole ovary, or the ovary and the fallopian tube on the same side. In some situations, the uterus is removed at the same time.

Imaging tests such as ultrasound, CT, or MRI can show an ovarian cyst, but they cannot confirm the diagnosis on their own. The firm, fibrous parts of a cystadenofibroma appear as solid areas on imaging. Solid areas raise concern for a borderline tumor or a cancer, so this tumor is sometimes suspected to be something more serious before surgery. Only examination of the tissue under the microscope settles the question.

During the operation, the surgeon may request an intraoperative consultation, also called a frozen section. The pathologist examines a piece of the tumor while the patient is still in the operating room and gives a preliminary diagnosis within minutes. That result can change the type of surgery performed. The pathologist makes the final diagnosis later, once the whole tumor has been examined in detail.

Mucinous tumors of the ovary can be very large, and different parts of one tumor can look different from each other. A single tumor can contain benign areas, borderline areas, and cancerous areas side by side. For that reason the pathologist samples these tumors thoroughly, commonly taking at least one tissue sample for every centimeter of the tumor, and more than that for very large tumors. This careful sampling is what allows the pathologist to say that the whole tumor is benign.

Mucinous tumors that start in the digestive tract can spread to the ovary and look very similar under the microscope. When the origin of a mucinous tumor is unclear, the pathologist may perform immunohistochemistry, a test that uses antibodies to detect specific proteins inside cells. A tumor that started in the ovary usually shows strong staining for CK7, with variable staining for CK20, and sometimes staining for PAX8. A tumor that spread from the bowel or appendix usually shows the reverse pattern, with strong CDX2 and SATB2 and little or no CK7. Not every case requires these tests. They are used only when the appearance under the microscope leaves the origin in doubt.

What does a mucinous cystadenofibroma look like under the microscope?

A mucinous cystadenofibroma is an ovarian tumor built from mucin-producing cysts and fibrous supporting tissue. To the naked eye, most look and feel like a balloon filled with thick fluid, with firm white areas in the wall. The inside may be one large space or many smaller ones. Under the microscope, the pathologist looks for several features:

Mucinous lining cells — The inside of the cysts is lined by a single, flat layer of tall cells that produce mucin. These cells resemble those that normally line parts of the digestive tract. The report may describe them as gastrointestinal-type or intestinal-type, and may mention goblet cells.
A prominent fibrous component — Thick walls and solid areas are made of fibrous supporting tissue, called stroma. This fibrous tissue is what separates a cystadenofibroma from a mucinous cystadenoma, which has thinner walls and less supporting tissue.
A simple, orderly lining — The lining cells form a thin, even layer. There is no crowding, no piling up of cells, and no complex branching growth.
No invasion — The lining cells stay where they belong and do not grow into the supporting tissue below. Absence of invasion is one finding that confirms the tumor is benign.

While examining the tumor, the pathologist also looks for two findings that are sometimes present in small amounts:

Focal atypia — Atypia is a word pathologists use for cells that look different from the cells normally found in a location. Most mucinous cystadenofibromas contain no atypical cells. When small areas of atypical cells are found, the report may describe a mucinous tumor with focal atypia.
Focal epithelial proliferation — In some tumors, small areas of the lining form more complex growths instead of a simple flat layer. When this is limited to small areas, the report may describe a mucinous tumor with focal epithelial proliferation.

When atypia or epithelial proliferation is confined to small focal areas, the tumor is still benign. If these areas are more extensive, the diagnosis changes to a mucinous borderline tumor. This is another reason pathologists sample mucinous tumors so thoroughly.

What other findings may be described in the report?

Along with the diagnosis of mucinous cystadenofibroma, your pathology report may describe other features of the tumor and the surrounding tissue.

Tumor size — The report gives the greatest dimension of the tumor in centimeters. Mucinous tumors of the ovary are often more than 10 cm across, and some are much larger. Size does not change the fact that the tumor is benign, but it does affect the type of surgery performed.
Tumor surface — Most mucinous cystadenofibromas have a smooth outer surface. The pathologist examines any growths or roughened areas on the surface closely to confirm they contain no abnormal cells.
Rupture — The report may note whether the cyst was intact or had ruptured, either before or during surgery. Rupture is not a concern in the way it is for a cancer, because a benign tumor does not spread. It is recorded because it is part of an accurate specimen description.
Other tumors in the same ovary — A mucinous tumor sometimes develops alongside another benign ovarian tumor. The two most common are a mature cystic teratoma and a Brenner tumor. Both are also noncancerous, and your report will name each one separately.

What happens after this diagnosis?

A mucinous cystadenofibroma is a benign ovarian tumor. It is not cancer, it does not spread to other parts of the body, and it is considered cured once it has been completely removed. What you and your gynecologic team discuss next depends on the size of the tumor, whether it caused symptoms, your age, and your overall situation. Points the team may raise include:

How much tissue was removed — Some tumors are removed by taking out the cyst alone and leaving the ovary in place. Others are removed together with the ovary and fallopian tube. The choice depends on the size of the tumor, your age, and your plans for future pregnancy.
Removal in one piece — Taking a large mucinous tumor out intact allows the pathologist to examine all of it. This is how the team confirms that no borderline or cancerous area was present anywhere in the tumor.
The possibility of a new cyst — When the ovary is left in place, a new cyst can develop there later. This is not a cancer coming back, because a mucinous cystadenofibroma is not cancer.
No chemotherapy or radiation — Treatments used for cancer are not used for this tumor, because it is benign.
Fertility — Removing one ovary does not usually prevent future pregnancy, since the other ovary continues to work. Your team can explain what your surgery means for you.

Most people need no further treatment after the tumor is removed. Your doctor will tell you whether any follow-up imaging or appointments are recommended in your situation.

Questions to ask your doctor

Was the diagnosis confirmed as a benign mucinous cystadenofibroma?
Were any borderline or cancerous areas found anywhere in the tumor?
How large was the tumor, and how many tissue samples were examined?
Were any areas of atypia or epithelial proliferation described in my report?
Was the tumor in one ovary only, or were both ovaries involved?
Was the entire cyst removed, or was only part of it removed?
Was the cyst intact when it was removed, or did it rupture?
Was the ovary or fallopian tube removed, and if so, why?
Were any other tumors, such as a teratoma or a Brenner tumor, found in the same ovary?
Were any extra tests done to confirm the tumor started in the ovary?
Could another cyst develop in the future, and would I need surgery again?
Do I need any follow-up imaging or appointments?
What symptoms should prompt me to contact you?