A cellular fibroma is a noncancerous (benign) tumor of the ovary. It grows from fibroblasts, the cells that make the firm supporting tissue found inside the ovary. It belongs to a family of tumors called sex cord-stromal tumors.
The word “cellular” describes what the pathologist sees under the microscope. In an ordinary ovarian fibroma, the tumor cells are spread apart in abundant collagen. In a cellular fibroma, the cells are packed more tightly together, with less collagen between them. That difference in density is the only thing that separates the two diagnoses. Both are benign and treated the same way.
Cellular fibromas occur most often in middle age, at an average of around 50 years. They range in size from under 1 cm to more than 20 cm, and almost all involve one ovary only. A cellular fibroma 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.
The cause of a cellular fibroma is not known. In most cases, there is no identifiable reason why one person develops this tumor.
A small number of ovarian fibromas of all types 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. Fibromas linked to the syndrome tend to occur at a younger age, involve both ovaries, form multiple separate nodules, and contain calcium deposits. Most cellular fibromas have nothing to do with Gorlin syndrome, and a single tumor in one ovary in an adult is not a reason to suspect it.
Many cellular fibromas cause no symptoms. Smaller tumors are often found by chance, either during an imaging test performed for another reason or when an ovary is removed for another reason. When symptoms do occur, they usually come from the size of the tumor.
A small number of people with a fibrous ovarian tumor develop fluid in both the abdomen and the chest. That combination is called Meigs syndrome. It closely resembles advanced ovarian cancer, and the blood test CA-125 can be raised as well. Many people in this situation are investigated for cancer before the diagnosis is known. The fluid clears on its own once the tumor is removed.
A cellular fibroma is diagnosed after the tumor is removed surgically and examined under the microscope by a pathologist. The surgery usually removes the whole ovary, sometimes along with the fallopian tube on the same side. In some cases, the tumor was not the reason for the operation and is found unexpectedly.
Imaging tests such as ultrasound, CT, or MRI show a firm, solid mass in the ovary. Imaging cannot reliably separate a cellular fibroma 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 samples the tumor in several places and pays close attention to two things: how often the tumor cells are dividing, and whether they look abnormal. These two findings separate a cellular fibroma from its close relatives and from a rare cancer called fibrosarcoma. Because both findings can vary from one part of a tumor to another, thorough sampling matters. When the appearance under the microscope could fit more than one diagnosis, additional stains may be performed, as described below.
A cellular fibroma is a benign ovarian tumor made of densely packed fibroblasts and the collagen they produce. To the naked eye, it is usually a firm, solid, white or pale tumor. Under the microscope, the pathologist looks for the following features.
Immunohistochemistry is a laboratory test that uses antibodies to detect specific proteins inside cells. For a cellular fibroma, these stains confirm that the spindle cells come from the supporting tissue of the ovary. They also separate this tumor from other spindle cell tumors that can look similar. If the tests were performed, the results appear in your report as a list of protein names with the word positive or negative beside each one.
Two further tests are used when the tumor is densely cellular, which is often the situation in a cellular fibroma. A reticulin stain outlines the fibers around individual cells, and the pattern differs between a fibrous tumor and an adult granulosa cell tumor. Testing for a change in a gene called FOXL2 can also help. That change is found in most adult granulosa cell tumors and is absent in cellular fibromas, so a negative result supports the benign diagnosis.
A cellular fibroma sits within a group of related ovarian tumors made of the same spindle cells. What separates them is how tightly the cells are packed, how often they divide, and whether they look abnormal. Your report may use any of the following terms.
The most important distinction is the last one. Frequent cell division alone does not make a tumor a fibrosarcoma. Under current World Health Organization criteria, clear nuclear abnormality must also be present. Tumors that divide often but look bland were once labeled fibrosarcoma, and patients were sometimes treated for a cancer they did not have. If your report says cellular fibroma, the pathologist looked for those abnormal features and did not find them.
Along with the diagnosis of cellular fibroma, your pathology report may describe other features of the tumor and the surrounding tissue.
A cellular fibroma 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 report findings, your age, and your overall situation. Points the team may raise include:
Your doctor will tell you what follow-up, if any, is recommended in your situation.