Endometrial cancer is diagnosed by taking a tissue sample from the lining of the uterus and examining it under a microscope. No blood test or imaging scan alone can confirm the diagnosis. The process typically starts when a woman reports abnormal vaginal bleeding, especially after menopause, and moves through ultrasound, biopsy, and sometimes additional procedures to determine the type and extent of cancer.
The Symptom That Starts the Process
Irregular vaginal bleeding is the most common first sign of endometrial cancer. For postmenopausal women, any vaginal bleeding is considered abnormal and worth investigating. For premenopausal women, the warning signs include unusually heavy periods, bleeding between periods, or a significant change in menstrual patterns.
Not every case of abnormal bleeding turns out to be cancer. About 9% of postmenopausal women who see a doctor for bleeding are ultimately diagnosed with endometrial cancer. That means the vast majority have a non-cancerous explanation: polyps, hormonal shifts, endometrial hyperplasia (an overgrowth of the uterine lining that isn’t yet cancer), or thinning of vaginal tissue. Still, 9% is high enough that bleeding after menopause always warrants evaluation.
Transvaginal Ultrasound as a First Step
The initial evaluation often begins with a transvaginal ultrasound. A small probe is placed in the vagina and uses sound waves to create images of the uterus, measuring the thickness of the endometrial lining. In postmenopausal women, a lining that measures 4 millimeters or less has a greater than 99% negative predictive value for endometrial cancer. In practical terms, if your lining is that thin, it’s extremely unlikely you have endometrial cancer.
A thicker lining doesn’t mean you have cancer. It means something is causing the lining to grow, and a tissue sample is needed to find out what. If the ultrasound can’t clearly visualize the lining, your doctor may recommend a follow-up procedure like a sonohysterogram (where fluid is injected into the uterus during ultrasound for a better view) or move directly to a biopsy.
One important caveat: certain aggressive types of endometrial cancer can develop even when the lining appears thin on ultrasound. If bleeding persists or recurs, a biopsy is recommended regardless of what the ultrasound shows.
Endometrial Biopsy: The Key Diagnostic Test
A tissue biopsy is the only way to definitively diagnose endometrial cancer. The most common approach is an office-based endometrial biopsy using a thin, flexible tube (often called a Pipelle) that’s inserted through the cervix to suction a small sample of tissue from the uterine lining. The procedure takes a few minutes and doesn’t require general anesthesia.
In postmenopausal women, this type of biopsy is 90% sensitive for detecting endometrial cancer, with a specificity near 100%. That means if the biopsy comes back positive, it’s almost certainly correct. If it comes back negative, there’s still a small chance something was missed, particularly if the cancer is in a small, localized area rather than spread across the lining. Pipelle biopsy detects about 75% of high-grade lesions but only about 23% of focal (localized) lesions, since it samples blindly rather than targeting a specific spot.
The procedure causes cramping that ranges from mild to quite uncomfortable. ACOG guidelines suggest that topical anesthetics and over-the-counter anti-inflammatory pain relievers taken beforehand may help reduce pain, though study results on the effectiveness of pain relievers for this procedure have been mixed. If you’re concerned about discomfort, ask your doctor ahead of time what options are available.
When a Biopsy Isn’t Enough
Sometimes the initial biopsy doesn’t provide a clear answer. The sample may be insufficient, the results inconclusive, or symptoms may persist despite a negative biopsy. In these cases, two additional procedures come into play.
Hysteroscopy involves inserting a thin, lighted camera through the cervix into the uterus. This lets the doctor visually inspect the uterine lining and target specific areas that look abnormal for biopsy, which is especially useful for catching focal lesions that a blind biopsy might miss.
Dilation and curettage (D&C) is a more thorough tissue sampling. The cervix is gently dilated and an instrument is used to scrape tissue from the uterine lining. This is typically done under sedation or anesthesia. D&C captures a broader sample than an office biopsy and detects about 67% of hyperplasia, 75% of high-grade lesions, and 37% of focal lesions. While neither method catches all focal lesions reliably, D&C and hysteroscopy together give a much more complete picture than a Pipelle biopsy alone.
Determining the Stage and Type
Once a biopsy confirms endometrial cancer, the next step is figuring out how far it has spread and what subtype it is. This information shapes the entire treatment plan.
Pelvic MRI is one of the most useful imaging tools at this stage. It accurately shows how deeply the cancer has grown into the muscular wall of the uterus (called myometrial invasion), whether it has reached the cervix, and whether nearby lymph nodes look suspicious. A CT scan of the chest, abdomen, and pelvis may also be ordered to check for spread to more distant areas.
The cancer is formally staged using the FIGO system, which was updated in 2023. The new staging system now incorporates not just the physical extent of the tumor but also its molecular profile. Pathologists test the tumor tissue for specific genetic markers: mutations in a gene called POLE, problems with the cell’s DNA repair system (called mismatch repair deficiency), and abnormalities in a protein called p53. These molecular features predict how the cancer will behave more accurately than tumor appearance alone.
Why this matters to you as a patient: molecular profiling directly affects treatment decisions. For example, tumors with POLE mutations tend to have excellent outcomes even without additional treatment after surgery. Tumors with p53 abnormalities, on the other hand, tend to be more aggressive and often require more intensive treatment. This molecular information helps your oncology team avoid both undertreating dangerous cancers and overtreating ones that are unlikely to cause further harm.
What the Diagnostic Timeline Looks Like
From the moment you report abnormal bleeding, the pace of diagnosis depends on which tests are needed. An ultrasound can often be done at the first visit or within days. If a biopsy is needed, it’s frequently performed in the office that same day or scheduled within a week or two. Biopsy results from the pathology lab typically take one to two weeks.
If the biopsy confirms cancer, staging with MRI and possibly CT scans adds another week or two. Molecular profiling of the tumor tissue may take additional time beyond the initial pathology report. In total, most women move from first symptom to a complete diagnosis and treatment plan within four to six weeks, though this varies by healthcare system and how straightforward the results are. If your initial biopsy is inconclusive and a D&C or hysteroscopy is needed, that adds time to the process.