## Histological Classification of Endometrial Cancer **Key Point:** Endometrioid adenocarcinoma accounts for approximately 70–80% of all endometrial cancers and is the most common histological type. ### Epidemiology and Associations | Histological Type | Frequency | Risk Factors | Prognosis | | --- | --- | --- | --- | | **Endometrioid adenocarcinoma** | 70–80% | Estrogen excess, obesity, PCOS, tamoxifen | Generally favorable (Stage I: 85–90% 5-year survival) | | Serous papillary carcinoma | 5–10% | Age, not estrogen-dependent | Poor (aggressive, early metastasis) | | Clear cell carcinoma | 2–5% | Age, not estrogen-dependent | Poor (aggressive behavior) | | Adenosquamous carcinoma | 2–5% | Mixed presentation | Intermediate to poor | **High-Yield:** Endometrioid carcinomas are **estrogen-dependent** and associated with endometrial hyperplasia (Type I cancers). They typically present at earlier stages (Stage I–II) and have better overall survival compared to non-endometrioid subtypes. ### Clinical Pearl **Clinical Pearl:** Endometrioid cancers often arise in the context of: - Unopposed estrogen exposure - Obesity (increased peripheral aromatization) - Polycystic ovary syndrome (PCOS) - Tamoxifen use (in breast cancer survivors) - Diabetes and hypertension ### Non-Endometrioid (Type II) Cancers Serous papillary and clear cell carcinomas are **estrogen-independent** (Type II cancers), occur in older women, and carry a much worse prognosis despite often presenting at earlier stages. They are more aggressive and prone to early myometrial invasion and extrauterine spread. **Mnemonic:** **SECC** — Serous, Endometrioid (most common), Clear cell, Carcinoma. But remember: **Endometrioid is the most frequent** (70–80%), while Serous and Clear cell are rare but aggressive.
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