Fibrothecoma of the Ovary: Understanding Your Pathology Report

Section Editor: Kianoosh Keyhanian MD FRCPC
August 31, 2026

A fibrothecoma is a noncancerous (benign) tumor of the ovary. It is made of a mixture of two cell types that are both normally found in the ovary. One is the fibroblast, a long, thin cell that forms the ovary’s firm supporting tissue. The other is the theca cell, a rounded hormone-producing cell that normally surrounds developing eggs. It belongs to a family of tumors called sex cord-stromal tumors.

The name reflects that mixture. A tumor made only of fibroblasts is called an ovarian fibroma. A tumor made only of theca cells is called a thecoma. When a pathologist sees a genuine mixture of both, the report may say fibrothecoma. All three are benign and are treated the same way.

These tumors occur most often around and after menopause, and almost all involve one ovary only. A fibrothecoma is not cancer, and it does not spread to other parts of the body. 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 fibrothecoma?

The cause of a fibrothecoma is not known. In most cases, there is no identifiable reason why one person develops this tumor.

A small number of tumors in this family occur as part of an inherited condition called nevoid basal cell carcinoma syndrome, also known as Gorlin syndrome. This syndrome is caused by a change in a gene called PTCH1, which normally helps limit how much cells grow. Tumors linked to the syndrome tend to occur at a younger age, involve both ovaries, form multiple separate nodules, and contain calcium deposits. Most fibrothecomas have nothing to do with Gorlin syndrome.

What are the symptoms?

Many fibrothecomas cause no symptoms and are found by chance during imaging or surgery performed for another reason. When symptoms occur, they come from two sources: the hormones the theca cells make, and the size of the tumor itself.

Bleeding after menopause — The theca cells in a fibrothecoma can make estrogen. In someone past menopause, extra estrogen thickens the lining of the uterus and can cause bleeding. A doctor should assess any bleeding after menopause.
Changes in menstrual bleeding — Before menopause, extra estrogen can cause heavy, prolonged, or irregular periods.
Male-pattern changes — A smaller number of these tumors make androgens, the male-type hormones. These can cause increased body or facial hair, thinning scalp hair, acne, a deeper voice, or periods stopping.
Abdominal or pelvic pain — A large tumor can cause discomfort or a feeling of pressure low in the abdomen.
Sudden, severe pain — A large ovarian tumor can twist on its blood supply, a problem called torsion. This causes sudden severe pain and needs urgent medical attention.

Hormone symptoms depend on how much theca cell tissue the tumor contains. A fibrothecoma with only a small thecomatous component may cause no hormone symptoms at all. Occasionally one of these tumors causes fluid to collect in the abdomen and around the lung, a combination called Meigs syndrome. This resembles advanced ovarian cancer, and the blood test CA-125 can be raised as well. The fluid clears once the tumor is removed.

How is the diagnosis made?

A fibrothecoma is diagnosed after the tumor is removed surgically and examined under the microscope by a pathologist. The surgery usually removes the whole ovary, often along with the fallopian tube on the same side. In someone past menopause, the uterus is sometimes removed at the same operation.

Imaging tests such as ultrasound, CT, or MRI show a firm, solid mass in the ovary. Imaging cannot separate a fibrothecoma from other solid ovarian tumors, including cancers. A solid ovarian mass on a scan is usually reported as needing surgery to establish the diagnosis. This is why many people are told a tumor is suspicious before the benign diagnosis is confirmed.

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 how much tissue the surgeon removes. The pathologist makes the final diagnosis later, once the whole tumor has been examined in detail.

The pathologist’s main task is to distinguish this tumor from others made of similar-looking cells, some of which are not benign. Additional stains and, in some cases, genetic testing are used for this purpose, as described below.

What does a fibrothecoma look like under the microscope?

A fibrothecoma is a benign ovarian tumor made of both fibroblasts and theca cells. To the naked eye, it is usually a firm, solid tumor. The cut surface is often white with yellow areas, reflecting the mixture: the white comes from collagen, and the yellow comes from fat stored inside the theca cells. Under the microscope, the pathologist looks for the following features.

Spindle cells — Long, thin cells called spindle cells, named for their tapered shape. They are usually arranged in bundles that cross one another and are surrounded by firm collagen. These are the fibroma-like areas.
Theca cells — Large rounded cells with abundant pale or pink-grey cytoplasm, the material that fills a cell around its center. The cytoplasm looks pale because it contains fat droplets. These cells are usually arranged in nests or broad sheets. These are the thecoma-like areas.
A genuine mixture — Both components are present in the same tumor, sometimes side by side and sometimes blended. The proportions vary widely from one tumor to another.
Round, uniform nuclei — The nucleus is the part of the cell that holds the genetic material. Marked variation in nuclear size and shape, called nuclear atypia, is not seen in a fibrothecoma.
Rare dividing cells — A cell caught in the act of dividing is called a mitotic figure. These should be rare.

Immunohistochemistry

Immunohistochemistry is a laboratory test that uses antibodies to detect specific proteins inside cells. For a fibrothecoma, these stains confirm that the tumor comes from the ovary’s supporting and hormone-producing cells. They also help separate it from other tumors that can look similar. If the tests were performed, your report lists the results as protein names with the word positive or negative beside each one.

Inhibin and calretinin. Positive, and often stronger in the theca cell areas than in the spindle cell areas. These proteins are made by the ovary’s hormone-producing cells. The uneven pattern fits a tumor with two components.
SF-1. Usually positive. SF-1, or steroidogenic factor 1, is present in cells that make steroid hormones.
WT1. Usually positive. WT1 is commonly present in tumors that arise from ovarian supporting tissue.
Estrogen receptor and progesterone receptor. Often positive. The estrogen receptor and progesterone receptor are proteins that respond to female hormones. A positive result is expected and does not mean hormone treatment is needed.
Cytokeratin. Usually negative. This protein is found in tumors that arise from lining cells. A negative result is important here, because a cancer that spread to the ovary from the stomach can closely mimic a fibrothecoma under the microscope.

Two further tests are used when the appearance overlaps with an adult granulosa cell tumor, which is a low-grade cancer. A reticulin stain outlines the fibers around the cells, and the pattern differs between the two tumors. Testing for a specific change in the gene FOXL2 is more definitive because that change is found in most adult granulosa cell tumors and is absent in fibrothecomas.

Why do reports use different names for these tumors?

Fibroma, thecoma, and fibrothecoma describe points along a single spectrum rather than three separate diseases. At one end are tumors made entirely of fibroblasts, and at the other are tumors made entirely of theca cells. Most tumors sit somewhere in between, and “fibrothecoma” is the term pathologists use for those.

Two things follow from this. First, the World Health Organization classification does not list fibrothecoma as a separate category. It recognizes fibroma and thecoma, and it treats mixed tumors as belonging to the same family. This is why you may find little written about fibrothecoma when you search for it, even though the word is used every day in pathology reports and radiology reports.

Second, two pathologists looking at the same tumor may reasonably choose different names, depending on how they weigh the proportions. This kind of disagreement is common with these tumors and is not a sign that anything has gone wrong. Because fibroma, thecoma, and fibrothecoma are all benign and treated by removing the tumor, the name does not change what happens next.

What does a fibrothecoma mean for the lining of the uterus?

Because the theca cells in a fibrothecoma can make estrogen, and estrogen makes the lining of the uterus grow, the endometrium deserves attention after this diagnosis. Thickening of the lining, called endometrial hyperplasia, and endometrial cancer have both been described in patients with hormone-producing tumors in this family.

If you have not already had an endometrial biopsy or a hysterectomy, your doctor may arrange for the lining to be checked, particularly if you had abnormal bleeding. If the uterus was removed at the same operation, your pathology report will describe the endometrium separately. Findings your report may describe include:

Normal endometrium — No abnormal growth is present.
Endometrial hyperplasia without atypia — The lining is thickened, and the glands are crowded, but the cells look normal. This is noncancerous and is usually treated with hormone therapy.
Endometrioid intraepithelial neoplasia — The glands are crowded,d and the cells look abnormal. This is a precancerous condition, also called atypical endometrial hyperplasia in older reports.
Endometrioid carcinoma — A cancer of the lining of the uterus.

A finding in the endometrium does not change the fact that the ovarian tumor itself is benign. The two diagnoses are reported and managed separately.

What other findings may be described in the report?

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

Tumor size — The report gives the greatest dimension in centimeters. Size does not change the fact that the tumor is benign, but it does influence the type of surgery performed.
Cut surface — The report often describes a white or yellow-white cut surface, reflecting a mixture of collagen and fat-containing cells.
One or both ovaries — Almost all of these tumors involve only one ovary. Involvement of both ovaries is unusual and prompts the pathologist to consider other diagnoses, including Gorlin syndrome in a younger patient.
Rupture and adhesions — The report may note whether the tumor was intact and whether it was stuck to nearby tissue. Rupture does not carry the significance it would for a cancer, because a benign tumor does not spread.
The other tissues removed — The report describes the fallopian tube and, when removed, the uterus, cervix, and other ovary. Each is reported separately.

What happens after this diagnosis?

A fibrothecoma is a benign ovarian tumor. It does not spread to other parts of the body, and complete surgical removal is the treatment. Because it is not cancer, it is not given a grade, and it is not assigned a stage. Grading and staging describe how a cancer is behaving and how far it has spread, and neither applies here.

What you and your gynecologic team discuss next depends on your age, whether the uterus was removed, and what the hormones were doing before surgery. Points the team may raise include:

Checking the lining of the uterus — If the uterus is still in place and you had abnormal bleeding, this is usually the first step after the diagnosis.
No chemotherapy or radiation — These treatments are not used for this tumor because it is benign.
Recurrence — A fibrothecoma does not come back once it has been completely removed.
Hormone symptoms settling — Abnormal bleeding usually stops once the tumor is removed. Male-pattern changes may take longer to improve, and some, such as a deeper voice, may not fully reverse.
Fertility — Removing one ovary does not usually prevent future pregnancy, since the other ovary continues to work. Fertility-sparing surgery is often possible for younger patients.

Most people need no further treatment for the ovarian tumor itself. Your doctor will tell you whether any follow-up is recommended in your situation.

Questions to ask your doctor

Was the diagnosis a fibrothecoma, a fibroma, or a thecoma, and does the difference matter for me?
Was there any concern that this could be a granulosa cell tumor or another type of cancer?
Were reticulin or FOXL2 tests performed, and what did they show?
Was the tumor making estrogen, androgens, or both?
Has the lining of my uterus been checked?
If my uterus was removed, what did the report say about the endometrium?
How large was the tumor?
Was the tumor in one ovary only, or were both ovaries involved?
Was the ovary removed, and was the fallopian tube removed as well?
Was the whole tumor removed?
Will my symptoms settle now that the tumor is out?
Does this affect my fertility?
Do I need any follow-up imaging or appointments?
What symptoms should prompt me to contact you?