A pelvic mass is any abnormal growth or swelling found in the lower abdomen, between the hip bones. Most are benign, ranging from ovarian cysts and uterine fibroids to inflammatory collections that resolve with medication. But because a small fraction turn out to be cancerous, and because even benign masses can cause pain, compress nearby organs, or twist on their blood supply, the discovery of one always warrants a careful workup. The challenge for both patients and clinicians is that pelvic masses from wildly different causes can look alike on initial imaging, sometimes mimicking cancer so convincingly that only surgery and a pathologist’s microscope settle the question.
The Most Common Benign Causes
If you’re told you have a pelvic mass, the most likely explanation by far is something non-cancerous. Ovarian cysts top the list. Many are “functional” cysts, meaning they form as a normal part of the menstrual cycle when a follicle doesn’t release its egg or doesn’t shrink after ovulation. These usually disappear on their own within a few weeks. Larger or persistent cysts, such as endometriomas (filled with old blood from endometriosis) or dermoid cysts (containing tissue like hair or fat), may stick around and grow, but they are still benign.
Uterine fibroids are another extremely common finding. These non-cancerous muscle tumors of the uterus can range from pea-sized to larger than a grapefruit. In a reported case, a 24-year-old woman had progressive abdominal enlargement over eleven months from a fibroid that had undergone cystic degeneration, making it look like a suspicious ovarian mass on imaging. Her blood marker CA-125 was elevated, adding further suspicion of malignancy, yet the surgical specimen turned out to be entirely benign.1Europe PMC. Diagnostic Challenge: Distinguishing Uterine Fibroid with Cystic Degeneration vs. Ovarian Cystic Malignancy. A Case Report. That story captures a recurring theme in pelvic-mass medicine: benign conditions regularly masquerade as something more sinister.
Endometriosis deserves its own mention. Endometrial tissue growing outside the uterus can form solid nodules or blood-filled cysts that enlarge over time. Deep infiltrating endometriosis, in particular, can invade the bowel wall or bladder and look alarming on MRI. One case documented a 10-centimeter mass in a pregnant woman with no prior endometriosis history. The mass was pressing against the rectum and looked malignant enough on imaging to prompt a biopsy, which revealed only decidualized endometriosis, a hormone-driven transformation of endometrial tissue during pregnancy. The mass vanished after delivery.2PubMed Central. Vanishing pelvic mass: Decidualized endometriosis during pregnancy
Infections That Mimic Cancer
Pelvic inflammatory disease and tubo-ovarian abscesses are among the trickiest benign imitators of ovarian cancer. When bacteria from a sexually transmitted or other pelvic infection cause pus-filled collections around the fallopian tubes and ovaries, the resulting mass can look complex and aggressive on ultrasound, CT, and even PET scans. In one case, a 20-year-old woman’s bilateral ovarian masses showed features strongly suspicious for malignancy on both MRI and PET/CT; surgical removal revealed only abscesses with no cancer whatsoever.3PubMed Central. Bilateral Tubo-Ovarian Abscess Mimics Ovarian Cancer on MRI and (18)F-FDG PET/CT
Adding to the confusion, tubo-ovarian abscesses can drive CA-125 levels sky-high. CA-125 is the blood marker most commonly used to flag ovarian cancer, but it rises in many non-cancerous conditions that irritate the peritoneum, the lining of the abdominal cavity. A case series from a tertiary cancer center in Egypt found that among 803 patients referred with suspicious ovarian masses, 41 turned out to have pelvic inflammatory disease after surgery. About 71 percent of those 41 had elevated CA-125, and the most common symptom was simply abdominal pain.4Indian Journal of Surgery. Pelvic Inflammatory Disease Mimicking Ovarian Cancer: A Case Series from A Tertiary Cancer Center The takeaway for patients: an elevated CA-125 with a pelvic mass does not automatically mean cancer, especially in younger women.5Journal of Obstetrics, Gynecology and Cancer Research. Tubo-Ovarian Abscess with Highly Elevated CA125 Level is Misdiagnosed as Ovarian Cancer: A Case Report
When the Source Is Not Gynecologic
Not every pelvic mass originates from the uterus or ovaries. The pelvis is a crowded space shared by the bladder, rectum, lymph nodes, nerves, and connective tissue. Masses arising from any of these structures can present the same way. A urologic case series of 22 large pelvic masses of unclear origin found a remarkable range of diagnoses after surgical removal, including schwannomas (nerve sheath tumors), leiomyosarcomas, lymphangiomas, chondrosarcoma, hydatid cysts, and even a sacral chordoma.6PubMed. Large pelvic masses of obscure origin: urologist’s perspective In another case, what appeared to be a typical pelvic mass on CT turned out to be an appendiceal adenocarcinoma that had already spread to the liver.7International Journal of Medical Science and Clinical Research Studies. Appendiceal Adenocarcinoma Presenting as a Pelvic Mass with Liver Metastasis: A Case Report
Men can develop pelvic masses too, though they are discussed less often. A 20-year-old man with chronic pelvic pain was found to have a retroperitoneal neurofibroma sitting above the bladder and invading its wall.8PubMed Central. Pelvic neurofibroma in a patient presenting with pelvic pain and urinary frequency: A case report Colorectal tumors, gastrointestinal stromal tumors, and soft-tissue sarcomas all appear in the pelvis across sexes.
Pelvic Masses During Pregnancy
Pelvic masses found during pregnancy create a particular kind of anxiety. Most are corpus luteum cysts or dermoid cysts discovered on routine first-trimester ultrasound, and they often resolve or remain stable without intervention. Occasionally, though, a mass is large enough to cause symptoms, raises concern for malignancy, or threatens a complication like torsion.
A rare but treacherous scenario is a chronic ectopic pregnancy presenting as a solid pelvic mass. Because chronic ectopic pregnancies produce very little pregnancy hormone (beta-hCG), the urine pregnancy test can come back negative, steering the clinical team away from the correct diagnosis. One case report described a woman with a weakly positive urine test and an extensive pelvic mass initially thought to be a fibroid; the actual problem was a chronic ectopic pregnancy with extensive adhesions.9PubMed Central. Chronic Ectopic Pregnancy Mimicking Broad Ligament Fibroid: A Case Report Early recognition matters because delaying surgery allows more scar tissue to form, making the eventual operation harder.
When surgery is needed during pregnancy, the approach matters. A study comparing laparoscopy (keyhole surgery) with open laparotomy for adnexal masses in pregnant women found that keyhole surgery led to shorter operative times (about 61 versus 70 minutes) and shorter hospital stays (about five versus seven days), with no significant difference in miscarriage or preterm delivery rates after adjusting for factors like gestational age and mass size.10PubMed. Laparotomy versus laparoscopy for the treatment of adnexal masses during pregnancy A separate study focusing specifically on adnexal torsion in pregnancy confirmed that laparoscopy produced less blood loss, fewer wound-healing problems, and shorter hospitalization compared with open surgery.11PubMed Central. Laparotomy versus laparoscopy for the treatment of adnexal torsion during pregnancy
Symptoms That Signal Urgency
Many pelvic masses grow slowly and silently, discovered by accident on imaging done for something else. But two acute presentations send people to the emergency department fast: ovarian torsion and ruptured ovarian cysts. Both cause sudden, sharp pelvic pain, and distinguishing between them on a physical exam alone is difficult.12Annals of Emergency Medicine. Ovarian Torsion versus Ruptured Ovarian Cyst: Emergency Department Presentation and Outcomes
Torsion happens when an ovary, often weighed down by a mass, twists on its stalk and cuts off its own blood supply. It occurs in roughly 2 to 15 percent of patients who undergo surgery for adnexal masses, and the most common symptom is sudden pelvic pain followed by nausea and vomiting.13PubMed Central. A review of ovary torsion Speed matters: if blood flow is not restored quickly, the ovary can die. A ruptured cyst, by contrast, is painful and sometimes causes internal bleeding, but is generally less dangerous. Both require rapid imaging, typically a transvaginal ultrasound with Doppler flow, to tell them apart.
Large masses can also cause more insidious complications. A pelvic endometriosis mass in one 45-year-old woman compressed the external iliac vein enough to trigger a deep vein thrombosis in her left leg, along with bilateral hydronephrosis from ureteral compression.14Journal of Vascular Surgery. Endovascular Management of Deep Vein Thrombosis Secondary to Pelvic Endometriosis Chronic symptoms like urinary frequency, constipation, or leg swelling can all be signs that a pelvic mass is pressing on adjacent structures.
How Doctors Determine What It Is
Pelvic ultrasound is the first-line imaging tool, and it often provides enough information to guide the next step. Ultrasound can show whether a mass is solid, fluid-filled (cystic), or a mix of both, and it can identify features that raise or lower concern for cancer, such as thick internal walls, irregular borders, or blood flow patterns.15PubMed Central. Assessment of adnexal masses using ultrasound: a practical review When ultrasound alone isn’t definitive, MRI becomes the tiebreaker.
To standardize how radiologists report what they see, the American College of Radiology developed the O-RADS MRI scoring system. It assigns masses a score from 1 to 5, with higher numbers indicating greater concern for malignancy.16PubMed Central. Ovarian/Adnexal Reporting and Data System for MRI (ORADS-MRI): Genesis and future directions In a validation study, experienced readers using O-RADS MRI achieved a sensitivity of 93 percent and specificity of 91 percent for distinguishing malignant from benign masses.17JAMA Network Open. Ovarian-Adnexal Reporting Data System Magnetic Resonance Imaging (O-RADS MRI) Score for Risk Stratification of Sonographically Indeterminate Adnexal Masses Those numbers are good but not perfect, which is why imaging alone rarely settles the question entirely.
Blood Markers and the ROMA Index
Blood tests supplement imaging. CA-125 is the oldest and best-known ovarian cancer marker, but as mentioned earlier, it rises in many non-cancerous conditions. A newer marker called HE4 tends to stay normal in benign disease but climbs in ovarian cancer, which makes it a useful companion test. In one study, HE4’s specificity and positive predictive value in premenopausal patients with ovarian cancer reached about 98 and 95 percent, respectively.18PubMed Central. The diagnostic value of serum HE4 and CA-125 and ROMA index in ovarian cancer
Combining CA-125 and HE4 into a formula called the ROMA index (Risk of Ovarian Malignancy Algorithm) improves accuracy beyond either test alone. A prospective multicenter study of 965 patients found that ROMA and HE4 performed especially well at distinguishing ovarian cancer from endometriosis, with sensitivity above 98 percent at 75 percent specificity, whereas CA-125 alone achieved only 75 percent sensitivity in that comparison.19PubMed Central. HE4 as a serum biomarker for the diagnosis of pelvic masses: a prospective, multicenter study in 965 patients A separate study confirmed that ROMA outperformed CA-125 alone in postmenopausal women.20PubMed. Comparison of HE4, CA125 and ROMA algorithm in women with a pelvic mass: correlation with pathological outcome
An important caveat: all three markers perform much better at detecting late-stage ovarian cancer than early-stage disease. The same multicenter study found that in stage I and II cancer, the diagnostic performance of CA-125, HE4, and ROMA all dropped below an acceptable threshold.19PubMed Central. HE4 as a serum biomarker for the diagnosis of pelvic masses: a prospective, multicenter study in 965 patients This means a normal blood test result does not rule out early ovarian cancer, so imaging and clinical judgment remain essential.
Treatment Depends on the Diagnosis and the Risk
There is no single treatment for “a pelvic mass” because the term covers such an enormous range of conditions. What happens next depends on whether the mass is likely benign or potentially malignant, whether it’s causing symptoms, and whether the patient is pregnant, trying to become pregnant, or postmenopausal.
- Watch and wait: Small, simple-looking ovarian cysts in premenopausal women often resolve on their own. Repeat ultrasound in six to eight weeks confirms whether the cyst has shrunk or disappeared.
- Medical management: Tubo-ovarian abscesses from pelvic inflammatory disease frequently respond to intravenous antibiotics, avoiding surgery altogether. Endometriosis-related masses may be managed with hormonal therapy.
- Minimally invasive surgery: When a mass needs to come out, laparoscopy is the preferred approach for most benign masses. It’s associated with shorter hospital stays, less pain, and faster recovery compared with open surgery.
- Open surgery: Very large masses, masses with features suspicious for cancer, or cases where the surgeon needs wide access for staging may require a traditional abdominal incision. If ovarian cancer is found, staging surgery and possible tumor debulking are part of the standard approach.
- Referral to a specialist: When imaging and blood markers suggest a high probability of malignancy, referral to a gynecologic oncologist before surgery improves outcomes. Proper staging and debulking at the first operation matter more than attempting a second surgery later.21PubMed Central. Management of the Adnexal Mass: Considerations for the Family Medicine Physician
Postmenopausal Masses and the Stability Question
A pelvic mass in a postmenopausal woman raises more concern than the same mass in a 25-year-old, because functional cysts (the most common benign explanation in younger women) essentially stop forming after menopause. The risk of malignancy goes up with age. But even in older women, most masses turn out to be benign.
A large study tracked over 4,000 older patients whose adnexal masses appeared stable on follow-up ultrasound at least six weeks after initial detection. Among those with stable masses, only 11 cancers were eventually diagnosed, a cumulative risk of about 0.27 percent. Patients whose masses changed on follow-up, by contrast, had a cancer risk of about 1.7 percent and were far more likely to need surgery. The cancer risk continued to drop with ongoing stability: by two years of unchanged imaging, the risk effectively reached zero in the study population.22American Journal of Obstetrics & Gynecology. Ovarian cancer risk among older patients with stable adnexal masses
This has real practical meaning. If you’re postmenopausal and have a small, simple-appearing cyst that looks the same on repeat imaging, the odds that it is cancer are very low. That doesn’t mean you should skip follow-up, but it does mean that immediate surgery isn’t always necessary. Your doctor may recommend periodic ultrasound surveillance instead, especially if the mass is small and shows no worrisome features.
Ovarian Cancer and Early Detection
The fear behind every pelvic mass evaluation is ovarian cancer. It’s not the most common gynecologic cancer, but it’s the deadliest, in large part because it rarely produces symptoms until it has already spread. Early-stage ovarian cancer is often found incidentally, when a mass is removed for another reason or picked up on imaging ordered for an unrelated complaint. A case study of high-grade serous ovarian cancer involving the fallopian tube underscored this reality: the patient’s tumor was caught at an early surgical stage, and delaying the evaluation further could have allowed the cancer to advance and worsened survival odds.23PubMed Central. High-grade serous ovarian cancer (HGSOC) with fallopian tube involvement
Researchers are working on better ways to detect ovarian cancer early. One emerging avenue involves analyzing lipid metabolites in pelvic fluid, with some metabolites showing strong correlations with clinical stage, fluid accumulation, lymph node spread, and recurrence.24PubMed. Lipid metabolites abnormally expressed in pelvic fluid as potential biomarkers for ovarian cancer: A case-control study These are early-stage research findings rather than tests available in your doctor’s office, but they point toward a future where the diagnostic gap between late-stage and early-stage detection might narrow.
Racial Disparities in Pelvic Mass Management
The medical conversation around pelvic masses doesn’t affect everyone equally. Research using large national cancer databases has shown that African American women with ovarian cancer have persistently higher mortality than white women, with the gap widening over time. After adjusting for factors like age, tumor stage, and access to surgery, the hazard ratio for death remained about 1.27 for African American women compared to white women.25PubMed. Have racial disparities in ovarian cancer increased over time? An analysis of SEER data
These disparities extend even to pediatric care. A study of children and adolescents with ovarian masses found that Black patients were significantly more likely to undergo oophorectomy, the complete removal of the ovary, compared to white patients, even though there were no differences in pre-operative workup, surgical management choices, or the final pathology of the masses.26Journal of Pediatric Surgery. Racial Disparities in Pediatric Ovarian Mass Management Losing an ovary in childhood has long-term implications for fertility and hormonal health, making this disparity especially concerning. The reasons behind these gaps are complex and likely involve differences in access to subspecialist care, implicit bias in clinical decision-making, and structural inequalities in the healthcare system, but the data makes clear that the problem exists and persists across age groups.