Patients are understandably confused when they find out that they have been diagnosed with a serous borderline tumor (SBT) of the ovary, which is also known as a serous tumor of low malignant potential or an atypical proliferative serous tumor. They might say, “C’mon, Doc, give it to me straight – Do I have cancer or don’t I?” It is important for patients to understand that not all tumors are classifiable as simply benign or malignant, just as it is not possible to accurately separate everyone by height if the only categories are short and tall or by the number of hairs on one’s head if the only categories are bald and not bald. SBTs show features under the microscope that are in between a benign serous tumor (serous cystadenoma) and a malignant serous tumor (serous carcinoma), analogous to many men who are best classified as “sorta bald.” The SBT is the prototypical borderline tumor, since its clinical behavior also straddles the border between benign and malignant, whereas the other types of ovarian borderline tumors may look worrisome under the microscope, but almost always behave in a benign fashion.
To put SBTs in context, ovarian serous neoplasms represent 30% of all ovarian tumors, and SBTs account for 10% of the tumors in this group. This means that SBTs represent about 3% of all ovarian tumors. Presenting signs and symptoms are nonspecific, and may include pelvic pain, discomfort, and/or a pelvic mass. Women with SBTs average 40-45 years of age. In roughly half of the cases, both ovaries are involved. About two-thirds of patients have stage I disease, whereas tumor has spread beyond the ovaries in the other third.
Normally, when an ovarian tumor has spread beyond the ovary, it is bad news. However, with SBTs, spread to peritoneal surfaces, lymph nodes, and the omentum is still often compatible with long-term survival, depending on the nature of these tumor deposits. To reflect this, spread beyond the ovaries by SBTs is referred to as “involvement” of these particular sites by tumor “implants.” Care is taken to avoid the use of the word “metastases,” which is reserved for spread by a full-fledged malignant tumor (cancer).
In patients with tumor implants beyond the ovary, treatment decisions and prognosis are dependent upon whether or not the implants are classified by the pathologist as noninvasive or invasive. This is a difficult and subjective area of gynecologic pathology, and this determination is best done by a pathologist with many years of experience in this area. Noninvasive implants, which are far more common than invasive implants, are associated with an excellent prognosis. In contrast, invasive implants are considered equivalent to metastatic low-grade carcinoma and are more likely to be associated with an adverse outcome. Patients with stage I SBTs and those with noninvasive implants are typically treated surgically and followed for the long term (recurrences can occur many years later and may take the form of invasive carcinoma). At least half of patients with SBTs with invasive implants of the classic type will eventually die of their disease, and it is this group of patients that may benefit from post-operative treatment with chemotherapy.