Neither clearly benign, nor truly malignant. Very favourable prognosis, often conservative surgery.
Borderline ovarian tumours — also called tumours of low malignant potential — account for approximately 15 to 20% of ovarian tumours operated on. They frequently occur in young women, sometimes discovered during a fertility work-up or a routine ultrasound. Their prognosis is generally very favourable, but they require surgery and rigorous follow-up.
You have a suspicious ovarian tumour and surgery is being considered? A pre-operative consultation allows us to define the best surgical strategy for your situation together.
Both affect the ovary, but their behaviour, treatment and prognosis differ considerably.
| Borderline tumour | Ovarian cancer | |
|---|---|---|
| Behaviour | Does not invade adjacent tissues | Invasive from the outset |
| Peritoneal deposits | Possible but most often non-invasive | Invasive carcinomatosis |
| Chemotherapy | Not indicated in routine | Standard treatment |
| Surgery | Often conservative (uterus & contralateral ovary preserved) | Extended cytoreductive surgery |
| Fertility | Often preserved | Generally compromised |
| 5-year survival | > 95% in most cases | Variable (30–70% depending on stage) |
| Follow-up | Long-term — 10 to 15 years minimum | 5 years intensive then adapted |
In the majority of cases, a borderline tumour produces no specific symptom. It is often discovered incidentally.
Pelvic ultrasound is the first examination. It shows an ovarian mass with suspicious characteristics — internal vegetations, a mixed solid and liquid appearance — that suggest a borderline tumour rather than a simple cyst.
Pelvic MRI clarifies the nature of the tumour and assesses any extension. A thoracoabdominopelvic CT scan looks for distant deposits.
The CA-125 marker may be slightly elevated, but it is often normal in borderline tumours — its absence of elevation is therefore not fully reassuring.
The definitive diagnosis is always made by the pathologist on analysis of the surgical specimen. It cannot be confirmed with certainty before the operation — which is why surgical planning is essential.
Serous borderline tumours are the most common. They can be bilateral — affecting both ovaries — and may be accompanied by peritoneal deposits. These deposits are most often non-invasive and of good prognosis. In rare cases, they can be invasive and require closer surveillance.
Mucinous borderline tumours are generally unilateral and large. When they are diagnosed, the first question is always: is this a primary ovarian tumour, or a metastasis from a digestive cancer? A colonoscopy or gastroscopy may be requested to rule this out.
Borderline tumours often occur without identifiable cause — but some factors appear to be associated with higher risk. These are not certain causes, but correlations observed in epidemiological studies.
Reproductive factors: nulliparity (never having given birth), infertility, early puberty or late menopause are associated with a slightly increased risk. Conversely, full-term pregnancies and breastfeeding appear to have a protective effect.
Gynaecological history: endometriosis is a recognised risk factor for certain types of ovarian tumours, including borderline tumours. BRCA1/2 mutations are primarily associated with invasive ovarian cancer; their specific role in borderline tumours is less clear.
Surgery is the only treatment for borderline tumours. No routine chemotherapy, no radiotherapy. The objective is to remove the tumour completely — while preserving, if possible, the uterus and the healthy ovary.
In young women with a desire for pregnancy, conservative surgery is often possible: only the affected ovary is removed (or the tumour if it is encapsulated), leaving the uterus and the healthy contralateral ovary. This approach allows subsequent pregnancies.
In women without a desire for pregnancy or after the menopause, surgery removes both ovaries, the fallopian tubes and the uterus — to eliminate all risk of recurrence on the remaining tissue.
Exploration of the abdomen is systematic — peritoneal deposits, the omentum (fatty apron), the peritoneal surfaces are all carefully inspected. This is intraoperative staging.
It happens that the borderline diagnosis is only made after the operation — a simple ovarian cyst was thought to be removed, and pathological analysis reveals a borderline tumour.
In this case, a multidisciplinary team meeting (MDT) discussion determines whether a second surgical procedure is necessary — to complete the exploration or remove remaining tissue — or whether surveillance alone is sufficient based on the tumour's characteristics and what was removed.
Re-operation is not always necessary. Each situation is evaluated individually.
Staging involves precisely assessing the extent of the disease at the time of surgery. It determines subsequent surveillance and, sometimes, the decision for a second procedure.
Peritoneal cytology: a sample of abdominal fluid is taken at the start of the procedure to look for free tumour cells. A simple but essential step.
Systematic exploration: the surgeon inspects the entire abdominal cavity — peritoneum, omentum, liver surface, paracolic gutters, diaphragmatic domes. Any suspicious deposit is biopsied.
Omentectomy: removal of the omentum is performed in most non-conservative surgeries. It allows for complete peritoneal staging.
Surgery is being proposed, or the diagnosis was made after the fact and you don't know whether a second procedure is necessary? A surgical opinion allows the situation to be reviewed.
Yes — in the vast majority of cases. Borderline tumours frequently affect women of childbearing age, and conservative surgery is precisely designed to allow subsequent pregnancies.
Pregnancies do occur after conservative surgery for borderline tumours — naturally or with assisted reproduction if necessary. The desire for pregnancy must be expressed before the operation so that the surgical strategy can be adapted.
If both ovaries are affected, ovarian stimulation or fertility preservation (egg or ovarian cortex freezing) can be discussed in a specialised consultation before surgery.
You wish to have a child and have just learned that you have a borderline tumour? Say so at the first consultation — it changes the surgical strategy.
The prognosis for borderline tumours is very favourable — but these tumours can recur several years, even more than a decade, after the operation. Follow-up therefore does not stop at 5 years.
First two years: consultations every 4 to 6 months with clinical examination, pelvic ultrasound and CA-125 measurement.
From 2 to 5 years: follow-up every 6 months. A CT scan may be performed depending on results or symptoms.
After 5 years: the pace eases to an annual consultation, but follow-up is maintained for 10 to 15 years minimum — sometimes lifelong in cases of conservative surgery, because the remaining ovary can develop a new tumour.
In cases of conservative surgery, the contralateral ovary is carefully monitored at each consultation by ultrasound.
The vast majority of recurrences occur again as borderline tumours — and are treated surgically, in the same way as the first time. The prognosis remains favourable.
Transformation into invasive carcinoma is possible but exceptional — it mainly concerns cases with invasive peritoneal deposits at the time of the initial diagnosis, or multiple recurrent forms. In the rare cases where peritoneal deposits are invasive, the tumour may be reclassified as low-grade serous adenocarcinoma — a distinct entity that then requires different management.
The very favourable prognosis of a borderline tumour is good news — but it can coexist with a real psychological burden. Knowing that surveillance must continue for 10 to 15 years, or even for life, is not without significance. The anxiety before each ultrasound, the fear of recurrence, questions about fertility: all of this is legitimate and deserves to be taken into account.
The diagnosis should not be minimised because it is "not really a cancer" — this is a frequent error, sometimes made by those around the patient, sometimes by healthcare professionals. A borderline tumour means surgery, surveillance, and a real impact on daily life. Acknowledging this is part of good care.
Psychological support, whether via a psycho-oncologist, a patient support group, or a general practitioner, can be very helpful during and after treatment.
In certain situations — advanced-stage borderline tumours, recurrence, or after completion of childbearing plans — completion surgery may include a hysterectomy with bilateral salpingo-oophorectomy. A complete dedicated page covers surgical approaches, complications and alternatives.
Discover the hysterectomy page →Come with your results, your questions, your concerns. We take the time to discuss everything together.