Ovarian Borderline Tumor (Low Malignant Potential): Diagnosis and Treatment — Overview, Diagnosis & Treatment Options | MyMedicPlus

Ovarian low malignant potential (LMP) tumors, also called borderline ovarian tumors, are a distinct category of ovarian epithelial neoplasms that display atypical proliferation and nuclear atypia beyond benign cystadenomas but lack destructive stromal invasion — the hallmark of invasive carcinoma. They account for approximately 15–20% of all epithelial ovarian tumors. The two dominant subtypes are serous borderline tumors (SBT, approximately 55%) and mucinous borderline tumors (MBT, approximately 40%), with rarer endometrioid, clear cell, and Brenner borderline subtypes. LMP tumors predominantly affect younger women, with a median age at diagnosis of 40–45 years — significantly younger than invasive epithelial ovarian cancer. The prognosis is generally excellent: 10-year survival exceeds 90% even for stage III disease. However, late recurrence (up to 20+ years after surgery) can occur, necessitating long-term follow-up.

The etiology of LMP tumors is not fully established, but molecular studies demonstrate distinct pathways from invasive high-grade serous carcinoma. Serous borderline tumors frequently harbor BRAF V600E and KRAS mutations, linking them to low-grade serous carcinoma rather than high-grade disease. Mucinous borderline tumors are associated with KRAS mutations and are more commonly bilateral when of intestinal rather than endocervical type. Risk factors overlap with those for invasive epithelial ovarian cancer: nulliparity, early menarche, late menopause, endometriosis (particularly for serous subtype), and family history of ovarian cancer. Protective factors include oral contraceptive use and multiparity. Unlike invasive carcinoma, BRCA1/2 mutations appear to play a smaller role in LMP tumor pathogenesis. Endometriosis-associated LMP tumors more commonly exhibit clear cell and endometrioid features.

Ovarian LMP tumors frequently produce symptoms related to their size, as they can grow quite large before detection. The most common presentations include pelvic or abdominal pain or discomfort, increasing abdominal girth, and a palpable pelvic mass. Bloating, early satiety, and urinary frequency or urgency may occur as the mass expands. Some patients are diagnosed incidentally during pelvic ultrasound performed for other reasons — this is particularly common with smaller tumors in younger women undergoing fertility workup. Mucinous borderline tumors may present with pseudomyxoma peritonei syndrome — progressive accumulation of mucin in the peritoneal cavity causing massive ascites, abdominal distension, and gastrointestinal obstruction — though true pseudomyxoma from ovarian primary is rare and usually reflects a primary appendiceal mucinous neoplasm. Unlike invasive ovarian cancer, constitutional symptoms such as weight loss and fatigue are less common at presentation.

Preoperative diagnosis relies primarily on pelvic ultrasound and MRI. Characteristic ultrasound findings include complex cystic masses with papillary projections, internal echoes, and septations without dense solid components. MRI better characterizes internal architecture. Serum CA-125 may be elevated but is not reliably diagnostic; HE4 and ROMA score add modest specificity. CT of abdomen and pelvis is used for staging assessment. Definitive diagnosis is histopathological and is made at the time of surgical resection — frozen section analysis during surgery guides surgical decision-making. The WHO classification distinguishes typical and micropapillary variants of serous LMP tumors; the micropapillary variant carries higher risk of invasive implants. Peritoneal implants — classified as invasive or non-invasive — are found in up to 30–40% of advanced serous LMP tumors and influence prognosis. FIGO staging parallels that of invasive ovarian carcinoma.

Surgery is the definitive treatment for ovarian LMP tumors; adjuvant chemotherapy has not demonstrated survival benefit and is not recommended in standard practice according to ESMO and NCCN guidelines. For women who have completed childbearing, comprehensive surgical staging — total abdominal hysterectomy, bilateral salpingo-oophorectomy, omentectomy, peritoneal biopsies — is the preferred approach. For younger women desiring fertility preservation, cystectomy (removal of the cyst while conserving the ovary) or unilateral salpingo-oophorectomy is acceptable even in stage I disease; recurrence rates after cystectomy are higher (15–20%) than after salpingo-oophorectomy (5–10%), but subsequent fertility and pregnancy rates are favorable. Laparoscopic surgery is appropriate for most stage I cases. Advanced-stage serous LMP with non-invasive peritoneal implants does not require chemotherapy; invasive implants may prompt individualized discussion of platinum-based chemotherapy, though evidence is limited. Completion staging surgery after initial cystectomy may be considered in high-risk cases.

Ovarian low malignant potential tumors carry an excellent prognosis substantially better than invasive epithelial ovarian carcinoma. Ten-year overall survival exceeds 90% even for advanced-stage (FIGO III) disease with non-invasive peritoneal implants. Stage I serous borderline tumors have a 10-year survival approaching 99%. Advanced-stage serous LMP tumors with non-invasive implants have recurrence rates of 15–30% over 10+ years, but recurrences are typically borderline (not invasive) and are surgically resectable with favorable outcomes. Transformation to invasive low-grade serous carcinoma occurs in fewer than 2% of borderline tumor cases overall, though the micropapillary variant of serous borderline tumor with invasive implants carries a higher transformation risk. Key prognostic factors include FIGO stage, presence of invasive (vs non-invasive) peritoneal implants, micropapillary growth pattern, and completeness of primary resection. Recurrence after complete surgical staging for stage I disease is under 5%; recurrence rates are higher after conservative cystectomy (15–20%) compared to salpingo-oophorectomy (5–10%). Late recurrences occurring 10–20+ years after diagnosis are well recognized and necessitate lifelong surveillance with annual pelvic examination, transvaginal ultrasound, and CA-125 monitoring for a minimum of 10 years. Fertility outcomes after conservative surgery are generally favorable — most women can conceive naturally or with assisted reproduction. Repeated surgery for recurrent disease is typically feasible and associated with good outcomes, given the non-aggressive nature of borderline recurrences.

There are no definitive preventive strategies specific to LMP tumors. General ovarian cancer risk-reduction measures — combined oral contraceptive pill use for 5+ years, multiparity, and breastfeeding — confer modest protective effects. Long-term surveillance after surgical treatment is essential given the risk of late recurrence: annual pelvic examination and transvaginal ultrasound, with CA-125 monitoring at each visit, are recommended for at least 10 years and ideally lifelong. Recurrences are most commonly borderline (not invasive), are often surgically resectable, and carry favorable outcomes with repeated surgery. Transformation to invasive carcinoma occurs in fewer than 2% of cases overall. Women who undergo fertility-sparing surgery should complete surgical staging (bilateral salpingo-oophorectomy and hysterectomy) once childbearing is complete, particularly for serous subtype with micropapillary features or invasive implants.

Women with a newly detected complex adnexal mass on ultrasound — especially one with papillary projections or internal echoes — should be referred to a gynecologic oncologist for evaluation before any surgical intervention. Symptoms of rapid abdominal enlargement, persistent pelvic pain, or early satiety in a woman of any age with a known or suspected ovarian mass warrant prompt specialist review. Young women with an incidentally detected ovarian cyst larger than 5 cm or with complex morphology should be seen by a gynecologist rather than managed expectantly. Women previously treated for LMP tumors experiencing new pelvic pain, increasing abdominal girth, or rising CA-125 levels during surveillance should be evaluated urgently for recurrence. Any woman who develops signs of bowel obstruction or massive ascites needs emergency assessment.