Can endometrial stromal neoplasms (ESN) mimic disordered proliferative endometrium or present with similar findings to fibroids in cases of abnormal uterine bleeding (AUB) with ultrasound (USG) findings suggestive of fibroids?

Endometrial Stromal Neoplasms: Diagnostic Mimicry and Clinical Presentation

Endometrial stromal neoplasms (ESN) can indeed mimic disordered proliferative endometrium and present with ultrasound findings suggestive of fibroids in patients with abnormal uterine bleeding, making them a critical diagnostic pitfall that requires tissue sampling for definitive diagnosis.

Clinical Presentation and Diagnostic Challenges

Overlapping Clinical Features

• ESN commonly presents with abnormal uterine bleeding, the same primary symptom as disordered proliferative endometrium and fibroids 1, 2.
• Patients typically present in the perimenopausal or postmenopausal age range (32-59 years), overlapping with the peak incidence of both dysfunctional bleeding patterns and fibroids 1, 3.
• Physical examination may reveal an enlarged uterus or pelvic mass, findings indistinguishable from leiomyomas on clinical assessment alone 3.

Imaging Limitations

Ultrasound cannot reliably distinguish ESN from benign pathology:

• Transvaginal ultrasound (TVUS) is sensitive for detecting structural abnormalities but cannot determine the specific etiology of endometrial thickening or masses 4.
• The presence of leiomyomas and adenomyosis can obscure complete visualization of the endometrium, potentially masking coexistent ESN 4.
• Sonohysterography, while excellent at distinguishing polyps from submucosal fibroids (97% accuracy), cannot differentiate benign from malignant endometrial pathology with certainty 4.

MRI Considerations

When ultrasound is inconclusive, MRI with diffusion-weighted imaging should be considered:

• MRI can identify malignant uterine pathology with sensitivity up to 79% for endometrial cancer and 100% for leiomyosarcomas 4.
• Diffusion-weighted imaging improves diagnostic accuracy for distinguishing benign from malignant lesions, with abnormal signal and irregularity of the endometrial-myometrial interface being key features 4.
• However, even MRI cannot definitively exclude ESN without tissue diagnosis 4.

Critical Diagnostic Algorithm

Mandatory Tissue Sampling Indications

Endometrial sampling or hysteroscopy with biopsy is required when:

• Any focal endometrial abnormality is identified on imaging, regardless of whether fibroids are also present 4.
• Endometrial thickness ≥5 mm in postmenopausal women with bleeding 4.
• Persistent or unexplained AUB despite negative initial imaging 4.
• Postmenopausal women with fibroids and bleeding must have endometrial cancer and uterine sarcoma excluded before any treatment 4.

Histopathologic Mimicry

ESN can be confused with benign proliferative patterns on histology:

• Myxoid and fibrous variants of ESN may lack typical stromal features, leading to misinterpretation 3.
• Disordered proliferative endometrium was the most common pathologic finding (20.5%) in one large series of AUB, highlighting how ESN could be overlooked if not specifically considered 5.
• Collision tumors (ESN with concurrent endometrioid adenocarcinoma) occur and require recognition of both components 2.

Common Pitfalls to Avoid

Do Not Assume Fibroids Explain All Symptoms

• The presence of fibroids on ultrasound does not exclude concurrent endometrial pathology, including ESN 4.
• In postmenopausal women, continued fibroid growth or bleeding should raise suspicion for uterine sarcoma, with risk increasing with age (up to 10.1 per 1,000 in women 75-79 years) 4.

Do Not Rely on Imaging Alone

• Neither ultrasound nor MRI can definitively distinguish ESN from benign conditions; tissue diagnosis is mandatory 4.
• If initial endometrial sampling is negative but symptoms persist, repeat imaging and sampling should be performed, as malignancies can be missed initially 4.

Recognize High-Risk Features

• Irregular endometrial-myometrial interface on imaging warrants aggressive tissue sampling 4.
• Heterogeneous echogenicity and abnormal vascularity patterns should prompt further investigation 4.

Treatment Implications

Accurate diagnosis is critical because ESN requires different management than benign conditions:

• Low-grade ESS requires total hysterectomy with bilateral salpingo-oophorectomy without morcellation 1.
• High-grade ESS and undifferentiated uterine sarcoma carry poor prognosis (median OS 11-24 months) and require aggressive surgical and adjuvant therapy 1.
• Morcellation is contraindicated when ESN is suspected, as it can upstage disease and worsen outcomes 4, 1.