A serous borderline tumor is an ovarian growth made up of cells that are more abnormal than those in a benign (harmless) cyst, but they have not become truly cancerous. For this reason, they are often called tumors of “low malignant potential.” This classification means they do not behave like invasive ovarian cancers because their cells have not invaded the supportive tissue of the ovary, known as the stroma.
These tumors represent about 10% to 20% of all epithelial ovarian tumors, which are growths arising from the surface layer of the ovary. They tend to be diagnosed in women at a younger age than invasive cancers, with a significant number of cases occurring in women under 40. They have some characteristics of cancer but lack the defining feature of invasion, placing them in a distinct category that requires careful management but often has a very positive outcome.
Diagnosis and Characteristics
The diagnosis of a serous borderline tumor often begins incidentally or with non-specific symptoms. Many individuals have no clear signs, and the tumor is discovered during a routine pelvic exam or an imaging scan performed for an unrelated issue. When symptoms are present, they are vague, such as pelvic pressure, abdominal bloating, or a feeling of fullness.
Initial diagnostic steps involve a physical examination and imaging studies. A transvaginal ultrasound is a common first step to visualize the ovaries and identify any abnormal masses. If a suspicious mass is found, a magnetic resonance imaging (MRI) scan may be ordered for a more detailed picture of the tumor’s characteristics. A blood test for the CA-125 tumor marker may also be performed, though its utility is limited as levels can be normal or only slightly elevated, making it an unreliable standalone diagnostic tool.
The definitive diagnosis is achieved through histopathology, which is the microscopic examination of the tumor tissue after it has been surgically removed. A pathologist analyzes a sample to look for atypical epithelial proliferation—meaning the cells on the tumor’s surface are abnormal and growing more than they should. The distinguishing feature is the absence of stromal invasion, confirming the tumor has not grown into the deeper connective tissue of the ovary. This lack of invasion is what separates a borderline tumor from an invasive carcinoma.
Surgical Treatment Options
Surgery is the primary and definitive treatment for serous borderline tumors, serving to remove the growth and confirm the diagnosis. The surgical approach is tailored to the individual, taking into account factors like age, the extent of the tumor, and the desire to have children. The goal is to remove the tumor completely while preserving reproductive function when possible.
Fertility-Sparing Surgery
For younger individuals who wish to preserve their ability to become pregnant, fertility-sparing surgery is the standard of care. This approach aims to remove only the affected tissue, leaving the uterus and at least a portion of one healthy ovary. The most common procedure is a unilateral salpingo-oophorectomy, where the entire affected ovary and fallopian tube are removed. In cases where the tumor is confined to a small area, a cystectomy, which involves removing only the tumor from the ovary, may be performed.
These conservative surgeries are safe and effective, offering an excellent prognosis without negatively impacting overall survival rates. The decision between a cystectomy and removing the entire ovary depends on the size and characteristics of the tumor, as well as the surgeon’s assessment during the operation. The priority is the complete removal of the tumor while safely preserving future fertility potential.
Extensive Surgery and Staging
For those who have completed childbearing or are postmenopausal, a more extensive surgical procedure is recommended. This involves a bilateral salpingo-oophorectomy (removal of both ovaries and fallopian tubes) and often a hysterectomy (removal of the uterus). This approach removes the primary tumor and eliminates the risk of a new borderline tumor developing in the remaining ovarian tissue.
Regardless of the extent of the primary surgery, a procedure known as surgical staging is performed at the same time. During staging, the surgeon inspects the abdominal cavity for any signs that tumor cells have spread. This involves taking multiple tissue samples (biopsies) from the peritoneum (the lining of the abdomen) and the omentum (a layer of fatty tissue). Peritoneal washings are also collected, where sterile fluid is rinsed inside the abdomen and then collected for microscopic analysis to determine the tumor’s extent.
Prognosis and Long-Term Management
The long-term outlook for individuals diagnosed with a serous borderline tumor is overwhelmingly positive, particularly when the tumor is confined to the ovary at the time of diagnosis. For these early-stage tumors, surgery is typically curative, and the vast majority of people go on to live a full life without further issues from the tumor.
Recurrence of a serous borderline tumor is possible, but it is not a common event. When a recurrence does happen, it is most often another borderline tumor rather than an invasive cancer, and these are treated with another surgery. Because of this small risk, long-term surveillance is a standard part of post-treatment care, involving regular pelvic exams and periodic imaging like transvaginal ultrasounds.
A factor that can influence the prognosis is the presence of invasive implants. In a small number of cases, staging may reveal that tumor cells have spread to the peritoneum and have begun to invade the tissue at these distant sites. The presence of invasive implants can change the tumor’s behavior and may require different management strategies. This finding is uncommon, as most serous borderline tumors do not have this feature.