8公分後腹膜腔腫瘤為首發表現的低級別子宮內膜間質肉瘤–案例報告

林子翔¹、張延驊^1,2,3

¹台北榮民總醫院 泌尿部；²陽明大學醫學院泌尿學科；³書田泌尿學研究中心

A 8cm Retroperitoneal Mass as the Initial Presentation of Low-Grade Endometrial Stromal Sarcoma : A Case Report

Tzu-Hsiang Lin¹, Yen-Hua Chang^1,2.3

¹Department of Urology, Taipei Veterans General Hospital, Taipei, Taiwan

²Department of Urology, School of Medicine, National Yang-Ming University, Taipei, Taiwan

³Shu-Tien Urological Institute, National Yang-Ming University, Taipei, Taiwan

Introduction

Endometrial stromal sarcomas (ESS) are rare uterine mesenchymal tumors that present significant diagnostic and therapeutic challenges due to their heterogeneous biological behavior. While recent histopathological and molecular advances have clarified the distinctions between Low-Grade (LG-ESS) and High-Grade (HG-ESS) subtypes—each carrying a unique prognosis—not all cases align neatly with these categories. Here, we present a clinical case of Stage IV LG-ESS that highlights these complexities.

Case Presentation

In September 2025, a 40-year-old female presented with acute-onset right lower limb swelling. Computed tomography (CT) identified a filling defect in the right external iliac vein, confirming deep vein thrombosis (DVT). Crucially, imaging also revealed an 8.5 x 6.0 x 5.5 cm complex adnexal mass with solid and cystic components, causing direct compression and potential invasion of the right external iliac vein.

Initial management included anticoagulation for the femoral DVT. While serum tumor markers were within normal limits, the tumor’s perceived unresectability prompted a CT-guided biopsy. Histopathology initially revealed a round cell neoplasm that could not be definitive classified via standard morphology and immunohistochemistry (IHC). However, Next-Generation Sequencing (NGS) identified a JAZF1-SUZ12 fusion, raising high suspicion for endometrial stromal sarcoma (ESS).

The patient underwent an en bloc tumor resection, total abdominal hysterectomy with bilateral salpingo-oophorectomy (TAH-BSO), right common iliac lymphadenectomy, and a right external iliac vein thrombectomy. Intraoperative findings included a large uterine leiomyoma exhibiting malignant behavior and a deep retroperitoneal tumor with extensive adhesions to the iliac vasculature.

Final pathology confirmed ESS originating from the endometrium with metastasis to the right common iliac lymph nodes. The specimen demonstrated lymphovascular invasion and positive margins at the retroperitoneal site. IHC staining was positive for CD10, ER (90%, strong expression), and WT1, consistent with a histological Grade 2 ESS.

The patient’s postoperative recovery was unremarkable. Adjuvant therapy was initiated one week post-surgery with an aromatase inhibitor, followed by doxorubicin (initially 80 mg) three weeks later. Due to severe emesis, the doxorubicin dose was titrated to 70 mg monthly. At present, the patient’s lower extremity edema has completely resolved, and she remains asymptomatic, denying abdominal pain or abnormal vaginal bleeding. Surveillance imaging is scheduled for the near future.

Discussions

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Refined Discussion

Endometrial stromal tumors (EST) are rare uterine mesenchymal malignancies with an annual incidence of approximately 0.30 per 100,000 women, primarily affecting perimenopausal and postmenopausal patients. According to current histopathological and molecular classifications, these are divided into four main categories: benign Endometrial Stromal Nodules (ESN), Low-Grade Endometrial Stromal Sarcoma (LG-ESS), High-Grade Endometrial Stromal Sarcoma (HG-ESS), and Undifferentiated Uterine Sarcoma (UUS).

In the present case, the tumor exhibited the JAZF1-SUZ12 fusion alongside diffuse, strong expression of estrogen receptors (ER) and CD10. These molecular markers, combined with the presence of lymphovascular invasion (LVSI), are characteristic of LG-ESS and are typically absent in HG-ESS and UUS. While the prognosis for LG-ESS is generally favorable—with a 5-year overall survival (OS) of 80–100% in early-stage disease—outcomes are heavily influenced by the FIGO stage. Our patient presented with FIGO Stage IV disease involving distant lymph nodes and a mitotic count of 10–19 mitoses per 10 HPF, suggesting a more aggressive clinical phenotype than standard low-grade presentations.

The gold standard for ESS management remains comprehensive surgical cytoreduction, including total abdominal hysterectomy and bilateral salpingo-oophorectomy (TAH-BSO). In this case, we also performed a right external iliac vein thrombectomy, resulting in the complete resolution of the patient's lower limb pitting edema. This aggressive surgical approach is supported by literature suggesting that complete resection of tumor thrombi correlates with improved survival. Conversely, adjuvant radiotherapy was deferred; current evidence suggests limited efficacy in the preoperative setting and a high risk of gastrointestinal toxicity due to the proximity of radiosensitive bowel loops.

The optimal adjuvant systemic therapy remains a subject of debate. While LG-ESS is traditionally managed with hormonal agents—such as aromatase inhibitors (AIs) or progestins—and HG-ESS typically warrants systemic chemotherapy, the aggressive features of our case (Stage IV and elevated mitotic index) prompted a multimodal approach. Consequently, we initiated a combined regimen of aromatase inhibitors and systemic chemotherapy to address both the hormonal sensitivity and the high-risk metastatic burden.

Conclusions

This case highlights that Stage IV LG-ESS can present with an aggressive clinical phenotype despite favorable molecular markers like the JAZF1-SUZ12 fusion. Our success with en bloc resection, vascular thrombectomy, and a multimodal adjuvant regimen (hormone therapy plus chemotherapy) demonstrates the necessity of intensifying treatment for high-risk presentations. Ultimately, management should be guided by FIGO stage and clinical behavior as much as histopathological grading. This underscores the importance of tailored, aggressive intervention to optimize outcomes in advanced-stage uterine sarcomas.

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