A 62-year-old woman with newly diagnosed endometrial cancer (Grade 2, endometrioid type) on endometrial biopsy is being staged. Pelvic examination is unremarkable. Which investigation is most appropriate for assessing myometrial invasion and determining surgical candidacy?

Explanation

## Preoperative Staging Investigation for Endometrial Cancer **Key Point:** MRI of the pelvis is the most appropriate imaging modality for assessing myometrial invasion, cervical stromal involvement, and local staging in endometrial cancer before surgical management. ### Why MRI Is Superior for Myometrial Assessment 1. **Highest soft-tissue contrast resolution** — distinguishes endometrium, myometrium, and serosa 2. **Accurate myometrial invasion assessment** — sensitivity 88–92% for detecting deep (>50%) invasion 3. **Cervical stromal involvement** — detects cervical invasion (Stage IB) 4. **Vaginal/parametrial extension** — identifies extrauterine spread 5. **Adnexal assessment** — evaluates ovaries and fallopian tubes 6. **No radiation exposure** — important for preoperative planning ### Imaging Modalities Comparison for Endometrial Cancer Staging | Modality | Myometrial Invasion | Cervical Involvement | Lymph Node Assessment | Cost | Radiation | Best Use | |---|---|---|---|---|---|---| | **MRI** | Excellent (88–92%) | Excellent | Limited | High | None | **Preoperative local staging** | | **CT** | Poor–Fair (60–70%) | Fair | Fair–Good | Moderate | Yes | Metastatic disease, advanced stage | | **Transvaginal US** | Fair (70–80%) | Fair | None | Low | None | Initial assessment, office-based | | **PET-CT** | Poor | Poor | Good | High | Yes | Recurrent/metastatic disease | **High-Yield:** MRI is the **imaging of choice for preoperative staging** of endometrial cancer to determine the extent of myometrial invasion, which guides the decision between simple hysterectomy (shallow invasion) vs. comprehensive staging with lymphadenectomy (deep invasion). **Mnemonic:** **MERIT** for MRI in Endometrial Cancer: - **M**yometrial invasion assessment (primary role) - **E**xtent of disease (local staging) - **R**ecognition of cervical involvement - **I**ntegrity of uterine serosa - **T**issue characterization (soft-tissue contrast) ### Clinical Context: When MRI Is Indicated - Preoperative staging of newly diagnosed endometrial cancer - Assessment of myometrial invasion depth (Grade 1–2 tumors, endometrioid type) - Evaluation for cervical stromal involvement (Stage IB) - Determination of surgical approach (simple vs. comprehensive staging) - Intermediate-risk disease (Grade 2, endometrioid type with myometrial invasion) ### When CT Is Used Instead - Metastatic workup (chest, abdomen, pelvis for distant spread) - Advanced-stage disease (Stage III–IV) - Contraindication to MRI (pacemaker, severe claustrophobia) - Assessment of para-aortic lymph nodes (though sensitivity is limited) **Clinical Pearl:** In this patient with Grade 2 endometrioid cancer, MRI is critical because intermediate-grade tumors have a 40–60% risk of myometrial invasion. The depth of invasion determines whether pelvic lymphadenectomy is needed, making accurate preoperative assessment essential for surgical planning.