Finding a mass on the ovary often raises the concern of cancer. The ovary can develop many types of growths, both cystic (fluid-filled) and solid, requiring a precise diagnosis to determine the mass’s nature. Understanding the specific type of ovarian growth helps medical professionals accurately assess the risk and plan appropriate management. The ovarian fibroma is a solid tumor that arises from the organ’s supportive tissues.
What Exactly Is an Ovarian Fibroma?
An ovarian fibroma is a benign, non-cancerous tumor developing from the connective tissue (stroma) of the ovary. Classified as a sex cord-stromal tumor, it is the most common solid tumor of the ovary, though it accounts for only about four percent of all ovarian neoplasms. These masses are firm, solid, and typically white or tan, characterized microscopically by bundles of spindle-shaped cells that produce collagen. Fibromas are generally slow-growing and are most commonly found in middle-aged women, often around age 52 during the perimenopausal or postmenopausal periods.
When small, the fibroma often remains asymptomatic and may be discovered incidentally during routine imaging. If symptoms occur, they usually involve pelvic discomfort, pain, or a feeling of pressure as the mass grows. In rare instances, the mass can cause the ovary to twist, a painful condition known as ovarian torsion, which requires immediate medical attention.
Cancer Risk and Malignant Transformation
Ovarian fibromas are overwhelmingly considered benign, non-cancerous growths. The vast majority pose no risk of malignancy and are curable with surgical removal. The concern about cancer arises because a very rare, highly aggressive, malignant counterpart exists: the ovarian fibrosarcoma.
True malignant transformation of a benign fibroma into a fibrosarcoma is exceedingly rare. Pathologists distinguish the two primarily by microscopic examination, looking at features like cellular atypia and the number of mitotic figures (cell divisions). A tumor with a mitotic count of three or fewer per ten high-power fields is considered a benign fibroma, while a higher count suggests a fibrosarcoma.
A common misconception about malignancy arises when a fibroma is associated with Meigs Syndrome. This syndrome is the classic triad of an ovarian fibroma, fluid accumulation in the abdomen (ascites), and fluid around the lungs (pleural effusion). This presentation closely mimics advanced ovarian cancer, which also presents with a pelvic mass and fluid buildup. Despite the alarming symptoms, the ovarian mass in Meigs Syndrome remains benign, and the symptoms resolve completely once the fibroma is surgically removed.
Differentiating Fibromas From Other Ovarian Masses
The primary challenge is differentiating a benign fibroma from other malignant solid ovarian masses before surgery. Imaging techniques, particularly ultrasound and Magnetic Resonance Imaging (MRI), are used to characterize the mass. While ultrasound is often the first tool used, MRI is frequently employed to gain more specific information due to its superior soft tissue resolution.
On MRI, fibromas typically appear as solid masses showing low signal intensity on T2-weighted images due to their dense, fibrous nature. This distinct appearance helps differentiate them from most malignant masses, which tend to have higher signal intensity. Diffusion-weighted imaging (DWI) also helps, as malignant lesions often exhibit lower apparent diffusion coefficient (ADC) values compared to benign lesions.
The serum CA-125 tumor marker is often elevated in epithelial ovarian cancer. In most cases of ovarian fibroma, the CA-125 level is normal or mildly elevated. However, CA-125 levels can be highly elevated in patients with Meigs Syndrome, complicating the distinction from cancer. In these cases, the elevation is not tumor-driven but is caused by irritation of the abdominal lining (peritoneum) due to the fluid present.
Managing and Treating Ovarian Fibromas
Management of an ovarian fibroma depends on the size of the mass and whether it is causing symptoms. For small, asymptomatic masses where the diagnosis is certain, watchful waiting with regular follow-up ultrasound examinations is appropriate. This approach avoids unnecessary intervention while monitoring the tumor for growth or change.
Surgical excision is the definitive treatment for fibromas that are symptomatic, growing rapidly, or large enough to potentially exclude malignancy. The goal of surgery is to remove the mass while aiming for ovarian preservation, especially in younger patients. This conservative approach, often involving a cystectomy or fibromectomy, is preferred to maintain fertility and hormonal function.
Minimally invasive techniques, such as laparoscopic surgery, are commonly used for removal, offering advantages like faster recovery and shorter hospital stays compared to traditional open surgery (laparotomy). For postmenopausal women or those without a desire for future fertility, the surgeon may recommend removing the entire ovary and fallopian tube (salpingo-oophorectomy). Since the fibroma is benign, surgical removal is curative, and associated symptoms, including those of Meigs Syndrome, resolve rapidly afterward.