Is an Endometrial Biopsy (EMB) necessary when the endometrium is noted to be thick on ultrasound?

From the Guidelines

Endometrial biopsy (EMB) is necessary when a thick endometrium is noted on ultrasound, particularly in postmenopausal women with endometrial thickness ≥5mm, as the negative predictive value for cancer is nearly 100% with an endometrial thickness of 4 mm or less 1. In postmenopausal women, a thickened endometrium (≥5 mm) generally prompts evaluation by endometrial tissue sampling 1. For premenopausal women, the decision to perform an EMB is more complex, as normal endometrial thickness varies with the phase of the menstrual cycle, and there is no validated absolute upper limit cutoff for endometrial thickness 1. However, in premenopausal women with risk factors for endometrial cancer, such as persistent abnormal uterine bleeding, obesity, PCOS, diabetes, or tamoxifen use, EMB is typically indicated when endometrial thickness exceeds 16mm or when there are concerning clinical features. The biopsy is essential to rule out endometrial hyperplasia or cancer, as ultrasound alone cannot reliably distinguish between benign and malignant causes of endometrial thickening 1. Some key points to consider when evaluating endometrial thickening include:

• The sensitivity and specificity of TVUS for diagnosing adenomyosis were 82.5% and 84.6%, respectively 1
• Detection of adenomyosis at TVUS may be limited if there is coexisting uterine pathology, such as leiomyomas 1
• Office endometrial biopsies have a false-negative rate of about 10%, thus a negative endometrial biopsy in a symptomatic patient must be followed by a fractional dilation and curettage (D&C) under anesthesia 1
• Hysteroscopy may be helpful in evaluating the endometrium for lesions, such as a polyp, if the patient has persistent or recurrent undiagnosed bleeding 1

From the Research

Endometrial Biopsy (EMB) Necessity

• The necessity of EMB when the endometrium is noted to be thick on ultrasound depends on various factors, including the patient's symptoms, medical history, and risk factors for endometrial cancer 2, 3.
• According to the studies, EMB is highly specific for diagnosing atypical hyperplasia and endometrial cancer in postmenopausal women, and it is recommended for postmenopausal women with uterine bleeding 2, 3.
• However, there is no consensus regarding which endometrial thickness cut-off should be used for recommending EMB in asymptomatic postmenopausal women 3.
• For women with abnormal uterine bleeding and risk factors for endometrial carcinoma, EMB should be offered 3.
• Hysteroscopy with EMB is useful in patients with abnormal bleeding, even without sonographic evidence of pathology, and it has high sensitivity for detecting intrauterine pathologies 3, 4.

Diagnostic Accuracy and Techniques

• The diagnostic accuracy of EMB can be affected by the technique used, with hysteroscopy being the targeted-biopsy method with the highest diagnostic accuracy and cost-effectiveness 3.
• Blind suction techniques are not reliable for the diagnosis of endometrial polyps, and hysteroscopic punch biopsy allows for the collection of only a limited amount of endometrial tissue 3, 4.
• The choice of biopsy technique depends on the patient's age, medical history, and the presence of risk factors for endometrial cancer 3, 5.

Clinical Practice Guidelines

• Clinical practice guidelines recommend EMB for the final diagnosis of chronic endometritis and for the evaluation of treatment outcomes in patients with early-stage endometrial cancer 3, 6.
• The guidelines also emphasize the importance of adequate tissue sampling and the use of topical cervical analgesia and oral nonsteroidal anti-inflammatory drugs to reduce procedure-associated pain 2, 5.