Uterine cancer develops in the tissue lining the uterus, called the endometrium. This is the most common cancer affecting the female reproductive organs. A pelvic ultrasound is a common, non-invasive imaging method utilized in gynecological practice to examine the uterus and surrounding structures. While the ultrasound cannot definitively diagnose cancer, it serves as an important first step in evaluating symptoms like abnormal bleeding. This imaging tool provides visual information that guides healthcare providers on whether more invasive testing is necessary.
How Pelvic Ultrasound Visualizes the Uterus
A pelvic ultrasound uses a transducer device that emits high-frequency sound waves. These sound waves travel through the body and bounce back as echoes when they meet tissues and organs. The transducer captures these echoes, and a computer translates them into real-time images called sonograms, allowing for the visualization of internal structures.
There are two primary ways a pelvic ultrasound is performed: the transabdominal approach and the transvaginal approach. For the transabdominal method, the transducer is moved across the lower abdomen, often requiring a full bladder to create an acoustic window for better viewing. The transvaginal ultrasound offers superior detail because a thin transducer is inserted directly into the vagina, positioning it closer to the target organs. This method provides a clearer view of the uterus, ovaries, fallopian tubes, and the inner lining of the uterus, the endometrium.
Indicators of Concern: What the Ultrasound Reveals
The pelvic ultrasound’s primary role in assessing for uterine cancer is to measure the thickness of the endometrium. This measurement is a crucial indicator, particularly for post-menopausal women experiencing abnormal vaginal bleeding. Uterine cancer causes the endometrial lining to become thicker than normal, a structural anomaly the ultrasound can visualize.
In a post-menopausal woman experiencing bleeding, an endometrial thickness of 5 millimeters or less suggests cancer is highly unlikely. If the measurement exceeds this 5 mm threshold, the risk of cancer increases, prompting further investigation. For post-menopausal women who are not experiencing bleeding, a measurement greater than 11 mm is considered a significant concern that warrants a biopsy. Other findings, such as an irregular texture of the endometrium, fluid within the uterine cavity, or abnormal growths like polyps or masses, can also raise suspicion.
The Limitations of Ultrasound in Cancer Diagnosis
The pelvic ultrasound is an imaging tool for risk assessment, not a definitive diagnostic test for cancer. The images only reveal physical characteristics, such as size and structure, and cannot determine the cellular makeup of the tissue. The limitation lies in its inability to distinguish a benign condition, like endometrial hyperplasia or fibroids, from malignant cancer cells.
A thickened endometrium is a sign that requires follow-up, but it is not proof of cancer. False-positive results, where the endometrium is thick but not cancerous, can occur in women taking certain medications, such as hormone replacement therapy. Conversely, the ultrasound can produce false-negative results, as some aggressive uterine cancers may not cause significant thickening, appearing as a thin line on the sonogram. Therefore, a normal-appearing ultrasound does not eliminate the possibility of cancer, especially in symptomatic patients.
Procedures for Definitive Uterine Cancer Confirmation
When an ultrasound indicates a high risk or a structural anomaly, the next step is to obtain a tissue sample for pathology testing. The only way to confirm a diagnosis of uterine cancer is through histological examination, where cells are analyzed under a microscope.
Endometrial Biopsy
The most common initial step is an endometrial biopsy, often performed in a doctor’s office. A thin, flexible tube is inserted through the cervix to suction a small amount of tissue from the lining.
Hysteroscopy
If the biopsy is inconclusive or if the provider needs to visualize the entire cavity, a hysteroscopy may be performed. This procedure involves inserting a narrow, lighted telescope-like instrument through the cervix to directly examine the inside of the uterus. During a hysteroscopy, the provider can precisely target and remove suspicious areas of tissue for sampling.
Dilation and Curettage (D&C)
A dilation and curettage (D&C) is a minor surgical procedure where the cervix is gently opened. A specialized instrument is used to scrape tissue from the uterine lining. This method is utilized if an office biopsy failed to provide sufficient tissue or if a more comprehensive sample is needed.