Endometrial hyperplasia is a pathology characterized by excessive proliferation of the endometrium resulting in diffuse or focal endometrial thickening. Unopposed estrogen stimulation (anovulation, obesity, tamoxifen, estrogen replacement) is the primary etiologic factor. Postmenopausal bleeding and premenopausal menorrhagia are the most common clinical presentations. Atypical hyperplasia is considered premalignant due to risk of progression to endometrial carcinoma (up to 30% progression rate). Imaging typically shows diffuse endometrial thickening, cystic changes, and homogeneous enhancement. Tamoxifen-associated hyperplasia shows characteristic 'Swiss cheese' appearance with subendometrial cystic changes.
Age Range
35-70
Peak Age
52
Gender
Female predominant
Prevalence
Common
Endometrial hyperplasia develops from excessive proliferation of endometrial glands and stroma due to unopposed estrogen stimulation. In normal menstrual cycle, estrogen thickens the endometrium during proliferative phase while progesterone provides secretory transformation balancing proliferation. Anovulation, obesity (androgen→estrogen conversion via aromatase from adipose tissue) or exogenous estrogen disrupts this balance. Histopathologically, increased number and size of glands, increased gland/stroma ratio and cystic dilation are observed. These cystic dilations manifest on imaging as 'Swiss cheese' or 'cystic endometrial thickening.' Tamoxifen shows anti-estrogenic effect on breast tissue while acting as partial estrogenic agonist on endometrium, creating characteristic imaging findings with subendometrial cystic changes. In atypical hyperplasia, nuclear atypia is added to glandular cells and malignant transformation risk significantly increases.
Multiple small cystic areas in the endometrium and subendometrial region with tamoxifen use — corresponding to dilated glands creating a Swiss cheese appearance. This pattern is highly characteristic of tamoxifen endometriopathy. Tamoxifen shows partial estrogenic agonist effect on endometrium causing glandular proliferation and cystic dilation. This finding prompts inquiry about tamoxifen use in postmenopausal breast cancer patients.
Diffuse endometrial thickening on transvaginal US — >5 mm double-layer thickness in postmenopausal women is accepted as diagnostic threshold. Endometrium shows homogeneous or mildly heterogeneous echogenicity. Endometrial-myometrial interface (junctional zone) is smoothly preserved. When focal thickening is present, endometrial polyp or submucosal myoma enters the differential.
Report Sentence
Diffuse endometrial thickening is observed with double-layer thickness measured as ... mm; consistent with endometrial hyperplasia.
Small anechoic cystic areas within thickened endometrium — corresponding to dilated glands. These cystic changes are particularly prominent with tamoxifen use, creating a 'Swiss cheese' appearance. Cystic areas located in the subendometrial region are characteristic of tamoxifen endometriopathy. Size of cystic changes may range from a few mm to 10-15 mm.
Report Sentence
Multiple cystic areas within the thickened endometrium, consistent with cystic endometrial hyperplasia / tamoxifen endometriopathy.
Diffuse endometrial thickening on T2-weighted images — endometrium shows high signal intensity on T2 (maintaining normal endometrial signal characteristics). Cystic changes are identified as markedly hyperintense areas on T2. Junctional zone (T2 hypointense band) is smoothly preserved — no myometrial invasion finding. T2 sequence is ideal for measuring endometrial thickness, evaluating cystic changes, and checking junctional zone integrity.
Report Sentence
Diffuse endometrial thickening with cystic changes on T2-weighted images with preserved junctional zone; consistent with endometrial hyperplasia.
Diffuse homogeneous enhancement of thickened endometrium on contrast-enhanced MRI. Enhancement pattern is smooth and uniform without focal irregular enhancement or non-enhancing necrotic areas. Resembles normal endometrial enhancement pattern but in thickened volume. Cystic areas do not show enhancement. Junctional zone is clearly assessed in contrast phase.
Report Sentence
Diffuse homogeneous enhancement of thickened endometrium on contrast-enhanced MRI without focal irregular enhancement or necrotic areas; consistent with benign endometrial hyperplasia.
Regular, symmetric vascular pattern in thickened endometrium on Doppler US. Distribution of normal endometrial spiral arterioles is preserved. Low-moderate flow velocities and moderate resistance index (RI 0.5-0.7) are observed. Chaotic or irregular neovascular pattern suggests malignancy and is not expected in hyperplasia.
Report Sentence
Regular vascular pattern in thickened endometrium on Doppler US without evidence of malignant neovascularization.
Hyperplastic endometrium does not show significant diffusion restriction on DWI — ADC values are generally >1.2 x 10^-3 mm2/s, higher than endometrial carcinoma. Mild DWI hyperintensity may be seen but is not accompanied by ADC decrease (T2 shine-through effect). When significant diffusion restriction is present, malignancy suspicion increases and biopsy is recommended.
Report Sentence
No significant diffusion restriction in thickened endometrium on DWI with preserved ADC values; finding favoring benign hyperplasia over malignancy.
Criteria
Increased number and size of glands, cystic dilation may be present but no nuclear atypia in glandular cells. Carcinoma progression risk is low (1-3%). Responds well to progestin therapy.
Distinct Features
Low malignancy risk, cystic changes may be prominent, responsive to progestin therapy, homogeneous thickening on imaging
Criteria
Nuclear atypia in glandular cells (large nuclei, prominent nucleoli, abnormal mitosis) is present. Carcinoma progression risk is high (up to 30%). Named endometrial intraepithelial neoplasia (EIN) in WHO 2020 classification. Cannot be reliably distinguished from simple hyperplasia on imaging — biopsy is mandatory.
Distinct Features
High malignancy risk, histopathological diagnosis required, indistinguishable from simple hyperplasia on imaging, hysterectomy should be considered
Criteria
Endometrial changes related to tamoxifen use — subendometrial cystic areas, endometrial thickening and polyp development. Tamoxifen shows partial estrogenic effect on endometrium. Characteristic 'Swiss cheese' pattern on imaging. Endometrial polyp, hyperplasia and rarely carcinoma may develop (up to 7% carcinoma risk with long-term use).
Distinct Features
Tamoxifen use history, subendometrial cystic changes, 'Swiss cheese' pattern, polyp may accompany, increased carcinoma risk
Distinguishing Feature
Type I endometrial carcinoma shows focal irregular thickening, heterogeneous enhancement and junctional zone disruption (myometrial invasion). Hyperplasia shows diffuse homogeneous thickening and preserved junctional zone. Carcinoma shows significant diffusion restriction on DWI (ADC <1.0 x 10^-3) while ADC values are higher in hyperplasia.
Distinguishing Feature
Endometrial polyp is a focal, well-defined endometrial mass typically showing a feeder vessel. Hyperplasia is diffuse endometrial thickening. SIS (saline infusion sonography) is very valuable in differentiating polyp from hyperplasia — polyp appears as a separate mass within the cavity while hyperplasia remains as diffuse thickening.
Distinguishing Feature
Submucosal leiomyoma is a well-defined T2 hypointense mass originating from myometrium growing toward the cavity. Endometrial hyperplasia originates from endometrium and is hyperintense on T2. The T2 hypointense solid mass of leiomyoma and the thickened hyperintense endometrial layer clearly distinguish these two entities on MRI.
Urgency
routineManagement
medicalBiopsy
NeededFollow-up
6-monthEndometrial hyperplasia diagnosis is suggested by imaging but endometrial biopsy (pipelle or dilation-curettage) is mandatory for definitive diagnosis and atypia assessment. Hyperplasia without atypia is managed medically with progestin therapy (3-6 months medroxyprogesterone acetate or levonorgestrel IUS). Atypical hyperplasia (EIN) should be considered for hysterectomy due to malignancy risk. Regular endometrial surveillance is recommended for tamoxifen users. Biopsy should be performed in all patients presenting with postmenopausal bleeding if endometrial thickness >5 mm.
Hyperplasia without atypia has low malignancy risk and may regress with progestin therapy. Atypical hyperplasia is a precursor to Type I endometrial carcinoma with 30% progression risk. Hysterectomy is recommended for patients who have completed fertility. If fertility preservation is desired, progestin therapy with close follow-up is applied.