Serous Cystadenoma of the Ovary: Understanding Your Pathology Report

Section Editor: Kianoosh Keyhanian MD FRCPC
May 25, 2026

A serous cystadenoma is a common, noncancerous (benign) type of ovarian tumor. It develops from the epithelium, the thin layer of cells that covers the surface of the ovary. A serous cystadenoma consists of one or more fluid-filled spaces called cysts and is lined by serous cells. Although a serous cystadenoma is not cancer and does not spread to other parts of the body, it can grow very large, and for this reason it sometimes causes noticeable symptoms. It is one of the most common benign tumors of the 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 serous cystadenoma?

The cause of a serous cystadenoma is not known. It is not caused by an infection and is not contagious. There are no clearly established lifestyle causes, and in most cases there is no identifiable reason why a particular person develops this type of tumor. Serous cystadenomas can occur at any age but are most often found in adult women, including during the reproductive years and around the time of menopause.

What are the symptoms?

Many serous cystadenomas cause no symptoms, particularly when they are small, and are discovered during an imaging test or examination performed for another reason. When symptoms do occur, they are usually related to the presence of a mass in the ovary and may include:

Abdominal or pelvic pain — Discomfort or pain in the lower abdomen or pelvis.
Abdominal swelling or bloating — A feeling of fullness, pressure, or an increase in abdominal size.
Pressure symptoms — A large cyst can press on nearby organs, sometimes causing changes in urination or bowel habits.

Because these symptoms are common and can have many causes, they are not specific to a serous cystadenoma. Any persistent abdominal or pelvic symptom should be evaluated by a doctor.

How is the diagnosis made?

For most women, the diagnosis of a serous cystadenoma is made after the tumor is surgically removed and sent to a pathologist for examination under the microscope. Depending on the situation, the fallopian tube on the same side, and sometimes the uterus, may be removed at the same time. Imaging tests such as ultrasound, CT, or MRI may show a cyst in the ovary, but they cannot confirm the diagnosis on their own; examining the tissue under the microscope allows the pathologist to confirm that the tumor is a benign serous cystadenoma rather than a borderline tumor or cancer.

During the operation, the surgeon may request an intraoperative consultation (also called a frozen section). In this situation, the pathologist examines a sample of the tumor while the patient is still in the operating room and provides a preliminary diagnosis within minutes. The result of an intraoperative consultation can change the type of surgery performed. A final diagnosis is made later, once the entire tumor has been examined in detail.

What does a serous cystadenoma look like under the microscope?

Most serous cystadenomas look and feel like a balloon filled with fluid. The inside of the tumor may be a single large space or several smaller spaces, all filled with fluid. Pathologists call these spaces cysts. When the tumor is examined under the microscope, several features are characteristic:

Serous lining cells — The inside of the cysts is lined by a single, flat layer of cells called serous cells. These cells produce the clear fluid that fills the tumor.
A simple, orderly lining — The lining cells form a thin, even layer without crowding, tufting, or complex finger-like projections. This simple appearance is what separates a benign serous cystadenoma from a serous borderline tumor, which shows more cellular crowding and complexity.
No abnormal (atypical) cells and no invasion — The cells look normal, and they do not grow into the supporting tissue of the ovary. These features confirm that the tumor is benign.
Adenofibroma pattern — Some tumors have thicker walls or solid areas that contain more supporting tissue and fewer cysts. These may be called a serous adenofibroma or serous cystadenofibroma. They are still completely benign.

What happens after this diagnosis?

A serous cystadenoma is benign. It is not cancer, it does not spread to other parts of the body, and it is not considered a condition that turns into ovarian cancer over time. Once the tumor has been completely removed, it is considered cured.

The discussion between you and your gynecologic team about treatment and follow-up depends on the size of the cyst, whether it is causing symptoms, your age, and your overall situation. Points the team may discuss include:

Surgical removal — Many serous cystadenomas are removed surgically, particularly when they are large or causing symptoms. The surgery may involve removing only the cyst or removing the affected ovary and fallopian tube, depending on the situation.
Monitoring — A small cyst that is not causing symptoms may sometimes be monitored with imaging over time rather than removed right away.
The possibility of a new cyst — When only the cyst is removed and the ovary is left in place, a new cyst can occasionally develop later. This is not a return of cancer, because a serous cystadenoma is not cancer.
No need for chemotherapy or radiation — Because a serous cystadenoma is benign, treatments used for cancer, such as chemotherapy and radiation therapy, are not needed.

Most people who have a serous cystadenoma removed need no further treatment. Your doctor will let you know whether any follow-up is recommended based on your individual situation.

Questions to ask your doctor

Was the tumor confined to one ovary, or were both ovaries involved?
Was the entire cyst removed, or was only part of it removed?
Was the diagnosis confirmed as a benign serous cystadenoma, with no borderline or cancerous areas?
Do I need any further treatment?
Is there a chance another cyst could develop in the future?
Do I need any follow-up imaging or appointments?
What symptoms should prompt me to contact you?