Endometrial carcinoma is classified into Type I and Type II categories. Which statement BEST differentiates Type II (serous) from Type I (endometrioid) endometrial carcinoma?

• A Type II occurs in obese, postmenopausal women and is driven by unopposed estrogen; Type I arises on atrophic endometrium in thin women
• B Type II is associated with Lynch syndrome (HNPCC) and shows microsatellite instability
• C Type I is associated with PTEN loss and arises from endometrial hyperplasia, while Type II arises from endometrial polyps
• D Type II is ER/PR-negative, TP53-mutated, arises on atrophic endometrium, and has worse prognosis than Type I ✓

Explanation

Type II (serous) endometrial carcinoma arises in an estrogen-independent manner on atrophic endometrium, typically in older, thin, post-menopausal women. Molecular hallmarks include TP53 mutations and HER2 amplification; tumors are ER/PR-negative. Despite early FIGO stage, serous carcinoma spreads intraperitoneally (similar to ovarian serous carcinoma) and has high recurrence rates with poor prognosis. Type I (endometrioid) carcinoma is ER/PR-positive, arises from complex atypical hyperplasia via PTEN loss and microsatellite instability (Lynch syndrome association), in the context of excess estrogen, and has better overall prognosis.

Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.

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