## Histological Types of Endometrial Carcinoma **Key Point:** Endometrioid adenocarcinoma accounts for approximately 70–80% of all endometrial malignancies, making it by far the most common type. ### Frequency Distribution | Histological Type | Frequency | Grade | Prognosis | | --- | --- | --- | --- | | **Endometrioid adenocarcinoma** | **70–80%** | **Usually low-grade (G1–G2)** | **Favorable** | | Serous (papillary) adenocarcinoma | 10–15% | High-grade (G3) | Poor | | Clear cell carcinoma | 4–5% | High-grade | Poor | | Mucinous adenocarcinoma | 1–2% | Variable | Intermediate | ### Clinical Features of Endometrioid Adenocarcinoma - **Association:** Strongly linked to unopposed estrogen exposure (obesity, PCOS, HRT without progestin) - **Grade:** Typically well-differentiated to moderately differentiated - **Stage at presentation:** Often early stage (Stage I–II) due to early vaginal bleeding - **5-year survival:** ~80% overall (varies by stage and grade) **High-Yield:** Endometrioid carcinoma is the prototype of **Type I endometrial cancer** (estrogen-dependent, low-grade, good prognosis). Serous and clear cell types are **Type II** (estrogen-independent, high-grade, aggressive). **Clinical Pearl:** A postmenopausal woman with abnormal bleeding and endometrial thickening on ultrasound should be biopsied; if adenocarcinoma is confirmed, endometrioid type is statistically most likely and carries a better prognosis than non-endometrioid subtypes. **Warning:** Do not confuse frequency with aggressiveness. Although serous carcinoma is rare (10–15%), it is far more aggressive than the common endometrioid type.
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