A 62-year-old obese (BMI 38), nulliparous, postmenopausal woman presents with painless postmenopausal bleeding for 6 weeks. Transvaginal ultrasound shows an endometrial stripe of 14 mm. Endometrial biopsy reveals well-differentiated endometrioid adenocarcinoma, FIGO grade 1. Hysterectomy specimen demonstrates the structure marked **A** in the diagram — a polypoid, friable, tan-white mass arising from the endometrium and projecting into the cavity, with focal superficial myometrial invasion (<50% myometrial thickness). Which of the following best describes the pathogenesis and molecular basis of this tumor type?
A. Serous adenocarcinoma with copy-number high TCGA profile, arising from unopposed estrogen exposure in obese women
B. Clear cell carcinoma with POLE ultramutated molecular signature, presenting as a polypoid mass with early myometrial invasion
C. Type I endometrial carcinoma arising from atypical hyperplasia in an estrogen-dependent setting, with PTEN/PI3K/KRAS/CTNNB1 mutations and MMR deficiency in 20–30%, carrying an excellent prognosis
D. Type II non-endometrioid carcinoma arising from atrophic endometrium in an estrogen-independent setting, with TP53 mutations and aggressive behavior
Explanation
Why Option 1 is correct
The polypoid endometrial mass marked A in the context of a 62-year-old obese, nulliparous, diabetic, postmenopausal woman with postmenopausal bleeding and well-differentiated endometrioid adenocarcinoma represents Type I endometrial carcinoma. This tumor arises from atypical hyperplasia in an estrogen-dependent setting due to unopposed estrogen from obesity and nulliparity. The molecular basis includes PTEN, PI3K, KRAS, and CTNNB1 mutations, with MMR deficiency present in 20–30% of cases. Type I tumors have an excellent prognosis, particularly when confined to the uterus with superficial myometrial invasion as seen here (FIGO stage IA). This classification and molecular profile are foundational to the Bokhman classification and TCGA molecular taxonomy (FIGO 2023, NCCN Guidelines).
Why each distractor is wrong
Option 2: Type II non-endometrioid carcinomas (serous and clear cell) arise from atrophic endometrium in an estrogen-independent setting and are associated with TP53 mutations. They present in older women and are aggressive. This patient has endometrioid histology, not serous or clear cell, and the clinical context (obesity, nulliparity) is classic for Type I, not Type II.
Option 3: Serous adenocarcinoma is a Type II histology with copy-number high TCGA profile and TP53 mutations. Although this patient is obese, serous carcinoma is estrogen-independent and arises from atrophic endometrium, not from atypical hyperplasia in an estrogen-dependent setting. The biopsy shows endometrioid, not serous, histology.
Option 4: POLE ultramutated signature is associated with excellent prognosis but is a distinct TCGA molecular class found in a small proportion of endometrial cancers. Clear cell carcinoma is a Type II non-endometrioid histology. The biopsy explicitly shows well-differentiated endometrioid adenocarcinoma, not clear cell carcinoma.
High-YieldNEET PG
Type I endometrial carcinoma (80% of cases) = endometrioid histology + estrogen-dependent + arises from atypical hyperplasia in obese/nulliparous/diabetic women + PTEN/PI3K/KRAS mutations + excellent prognosis; Type II = non-endometrioid (serous/clear cell) + estrogen-independent + TP53 mutations + aggressive.
