Uterine cancer, most commonly endometrial cancer, originates in the lining of the uterus, known as the endometrium. When symptoms like abnormal vaginal bleeding, particularly after menopause, occur, an ultrasound is typically the first step in investigation. This non-invasive imaging technique uses sound waves to create a visual map of the uterus and surrounding structures. The scan helps doctors determine whether further, more definitive testing is necessary to confirm or rule out cancer.
The Role of Ultrasound in Uterine Evaluation
Ultrasound serves as a rapid, accessible, and cost-effective method for initial uterine assessment. It allows for real-time visualization of the uterus, its muscular wall (myometrium), and the inner lining (endometrium) without radiation exposure.
The preferred method is a Transvaginal Ultrasound (TVUS), where a small transducer is gently inserted into the vagina. This positioning provides a much closer view of the uterus and endometrium than a transabdominal scan. The high-resolution images allow the sonographer to accurately measure the endometrial stripe and examine the texture of the uterine tissues.
The sonographer examines the endometrium for any abnormal thickening or masses, while also assessing the depth of the myometrium. Sometimes, a saline infusion sonohysterography (SIS) is performed, which involves injecting sterile salt water into the uterus during the TVUS. This fluid gently distends the uterine cavity, providing clearer contrast to better visualize the lining and any potential growths.
The Critical Marker: Measuring Endometrial Thickness
The measurement of the endometrial stripe is often the most significant finding in an ultrasound for potential uterine cancer. The endometrial stripe is the visualization of the uterine lining, measured at its thickest point from one side of the basal layer to the other.
For pre-menopausal women, the thickness of the endometrium naturally changes throughout the menstrual cycle, ranging from 2 millimeters up to 16 millimeters. Because of this natural fluctuation, the measurement is a less reliable screening tool for this group. In post-menopausal women, however, the endometrium is expected to be thin and stable.
A measurement of the endometrial stripe greater than 4 or 5 millimeters in a post-menopausal woman experiencing vaginal bleeding is considered abnormal. This increased thickness suggests an abnormal proliferation of cells, which could be benign conditions like polyps or hyperplasia, or it could be cancer. The risk of cancer increases when the measurement exceeds this threshold in the presence of bleeding.
Identifying Other Key Visual Indicators
Beyond the thickness measurement, the visual quality of the endometrial tissue provides additional clues. Cancerous tissue often appears as a heterogeneous mass, meaning it has a mixed texture with both bright and dark areas. The mass may be described as polypoid, appearing as a distinct, lump-like growth that fills the uterine cavity.
The borders of the suspicious area may also appear irregular or ill-defined, suggesting that the growth is invading the surrounding myometrium (the muscle layer of the uterus). Another finding associated with a tumor is the presence of fluid within the uterine cavity, such as hematometra (blood) or pyometra (pus). This fluid collection suggests an obstruction of the cervical canal, which a tumor can cause.
Using Color Doppler ultrasound, the technician assesses the blood flow within the suspicious area. Increased vascularity, appearing as multiple branching vessels within the mass, can indicate that the tissue is abnormal. These qualitative findings supplement the thickness measurement and help doctors decide on the next steps in evaluation.
Confirming the Diagnosis: Procedures Following an Abnormal Scan
An ultrasound is a screening tool; it can suggest the possibility of uterine cancer, but it cannot definitively diagnose it. If the scan reveals a suspicious finding, such as an endometrial stripe measurement over the threshold, the next step is to obtain a tissue sample. This is necessary because many conditions, including benign polyps or simple hyperplasia, can also cause endometrial thickening.
The most common procedure for tissue sampling is an Endometrial Biopsy, often performed in a doctor’s office using a thin, flexible tube to suction tissue from the uterine lining. If the biopsy is inconclusive or a better view of the cavity is needed, a Hysteroscopy with Dilation and Curettage (D&C) may be performed. Hysteroscopy involves inserting a tiny camera into the uterus to directly visualize and sample the entire lining.
Only the pathological examination of the tissue sample under a microscope can confirm the presence of cancer cells. The ultrasound acts as the initial guide, alerting the medical team that a deeper investigation is required to establish a final diagnosis.