A 62-year-old woman from Mumbai presents with postmenopausal bleeding for 6 weeks. She has a history of tamoxifen use for breast cancer (treated 8 years ago). Pelvic ultrasound shows an endometrial thickness of 22 mm with a heterogeneous mass. Hysteroscopy and endometrial biopsy reveal endometrial adenocarcinoma, grade 2, with invasion limited to the inner third of the myometrium. MRI pelvis shows no evidence of cervical involvement or extrauterine disease. What is the FIGO 2009 stage of this tumor?

Explanation

## Clinical Context & Risk Factors **Key Point:** Tamoxifen use is a well-established risk factor for endometrial carcinoma, increasing risk 2–3 fold. This patient's presentation (postmenopausal bleeding, endometrial thickening, adenocarcinoma) is classic for tamoxifen-associated endometrial cancer. ## FIGO 2009 Staging for Endometrial Carcinoma The FIGO 2009 staging system is based on **surgical-pathological findings**. Key anatomical criteria: | Stage | Criteria | |-------|----------| | **IA** | Tumor confined to uterus; **no or less than 50% myometrial invasion** | | **IB** | Tumor confined to uterus; **≥50% myometrial invasion** | | **II** | Cervical stromal involvement; **no parametrial spread** | | **IIIA** | Tumor invades serosa and/or adnexa | | **IIIB** | Vaginal and/or parametrial involvement | | **IIIC1** | Pelvic lymph node metastases | | **IIIC2** | Para-aortic lymph node metastases | | **IVA** | Tumor invasion of bladder and/or bowel mucosa | | **IVB** | Distant metastases | ## Analysis of This Case 1. **Myometrial invasion:** "Limited to the inner third of the myometrium" = **<50% myometrial invasion** → Stage IA or IB criterion met. 2. **Cervical involvement:** MRI shows "no evidence of cervical involvement" → Excludes Stage II. 3. **Extrauterine disease:** "No extrauterine disease" on MRI → Excludes Stage III and IV. 4. **Depth of invasion:** Inner third of myometrium is clearly **<50% invasion** → **Stage IA**. **Clinical Pearl:** In the FIGO 2009 system, the **depth of myometrial invasion** is the most critical determinant of stage in early-stage disease. Invasion of <50% (inner half) = Stage IA; ≥50% (outer half) = Stage IB. This is a major prognostic factor, as deeper invasion correlates with increased risk of lymph node metastases and recurrence. **High-Yield:** The distinction between Stage IA and IB is crucial for treatment planning. Stage IA tumors (especially grade 1–2) may be managed with surgery alone, whereas Stage IB tumors typically warrant adjuvant therapy (radiation ± chemotherapy). ## Why Not Other Stages? - **Stage IB:** Requires ≥50% myometrial invasion. This tumor invades only the inner third, so it does not meet this criterion. - **Stage II:** Requires cervical stromal involvement. MRI explicitly excludes cervical involvement. - **Stage IIIA and beyond:** Require extrauterine spread (serosa, adnexa, lymph nodes, etc.), which is absent on imaging and biopsy.