A pelvic mass is a growth or lump found in the lower abdomen and pelvic region, often discovered incidentally during a routine examination or imaging. While the discovery raises concerns about cancer, the mass may originate from reproductive organs like the uterus or ovaries, or surrounding structures such as the bowel or bladder. This article examines the likelihood of a pelvic mass being cancerous and details the factors that influence this probability.
Overall Malignancy Rates and Prevalence
The vast majority of pelvic masses detected in women are benign. The probability of malignancy heavily depends on a woman’s age and menopausal status, which is the most significant differentiating factor. For premenopausal women, the risk of a pelvic mass being cancerous is low, generally estimated between 1% and 7.9% in studies of adnexal masses. This risk increases notably after menopause, when functional cysts become less common. In postmenopausal women, the likelihood of malignancy ranges from approximately 11.9% to as high as 37.6%. Ovarian cancer, a common source of malignant pelvic masses, has a lifetime risk of 1.42%, with the greatest risk occurring after menopause.
Identifying Common Non-Cancerous Pelvic Masses
The low malignancy rate in premenopausal women is due to the high prevalence of functional masses tied to the menstrual cycle. The most frequent benign growth is the uterine fibroid, also known as a leiomyoma, which originates in the muscular wall of the uterus. Fibroids are found in at least 20% of reproductive-aged women and may cause symptoms like heavy menstrual bleeding or pelvic pressure, though they are often asymptomatic.
Functional ovarian cysts are also common and include follicular cysts and corpus luteum cysts. Follicular cysts develop when the follicle fails to rupture and typically resolve spontaneously. Other benign ovarian masses include endometriomas (cysts formed by endometrial tissue) and cystic teratomas (dermoid cysts), which are the most common ovarian neoplasm in women under 40. These growths are generally characterized by their simple, fluid-filled appearance on imaging, helping distinguish them from complex masses.
Key Indicators That Increase Cancer Risk
Clinical assessment focuses on specific characteristics and symptoms that raise suspicion for malignancy. Age is a strong indicator, as postmenopausal women with a pelvic mass have a greater chance of cancer than younger counterparts. Imaging, such as ultrasound, provides physical characteristics of the mass. Features suggesting malignancy include:
- Presence of solid components
- Thick internal walls or septations
- Irregular shape
- Detection of blood flow within solid parts using Doppler imaging
- Fluid in the abdomen (ascites)
- Evidence of growth extending beyond the pelvis
Symptoms also warrant investigation, especially if persistent. These include new-onset pelvic or abdominal pain, bloating, unexplained weight loss, or changes in urinary and bowel habits.
The Diagnostic Process for Confirmation
Once a mass is identified, the initial step is transvaginal ultrasonography, the standard imaging modality used to evaluate the mass’s structure. This imaging helps determine if the mass is a simple cyst, which is benign, or if it exhibits complex features suggesting malignancy. If the ultrasound is inconclusive or suspicious, a Magnetic Resonance Imaging (MRI) scan may be utilized for further detailed characterization.
Blood tests are employed to assess tumor markers, such as Cancer Antigen 125 (CA-125). While CA-125 is frequently elevated in ovarian cancer, it is not a perfect screening tool because it can also be raised by many benign conditions, including endometriosis and fibroids. For postmenopausal women with a concerning mass, an elevated CA-125 level contributes to risk assessment. However, the definitive diagnosis requires a tissue sample obtained either through a biopsy or surgical removal, allowing a pathologist to examine the cells.