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Endometrial Cancer for USMLE Step 1

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Endometrial Cancer for the USMLE Step 1 Exam
Definition and Epidemiology
  • Definition
    • Endometrial cancer arises from the lining of the uterus (endometrium) and is the most common gynecologic malignancy in the United States.
    • Two primary types:
    • Type I (Endometrioid): Estrogen-dependent, associated with endometrial hyperplasia, accounts for 80-90% of cases.
    • Type II (Non-endometrioid): Estrogen-independent, includes serous and clear cell types, and has a more aggressive course.
  • Epidemiology
    • Primarily affects postmenopausal women, with a peak incidence between ages 55-65.
    • The incidence is rising, partly due to increased obesity rates.
Risk Factors
  • Hormonal Factors:
    • Unopposed Estrogen: Chronic estrogen exposure without progesterone, which stimulates endometrial proliferation.
    • Obesity: Increased peripheral conversion of androgens to estrogens in adipose tissue.
    • Polycystic Ovarian Syndrome (PCOS): Anovulation leads to unopposed estrogen stimulation of the endometrium.
  • Genetic Predisposition:
    • Lynch Syndrome (HNPCC): Hereditary nonpolyposis colorectal cancer increases the risk for endometrial cancer.
    • Cowden Syndrome: Associated with PTEN gene mutations, linked to multiple cancers, including endometrial cancer.
  • Other Factors:
    • Early Menarche and Late Menopause: Prolonged exposure to estrogen.
    • Nulliparity: Lack of progesterone exposure during pregnancy.
    • Tamoxifen Use: Partial estrogen agonist effect on the endometrium.
Pathophysiology
  • Type I Pathway:
    • Excess estrogen causes endometrial hyperplasia, which can progress to atypical hyperplasia and then to endometrioid carcinoma.
    • Associated with mutations in PTEN, KRAS, and microsatellite instability.
Endometrioid Cancer Pathophysiology
  • Type II Pathway:
    • Not linked to estrogen and arises from an atrophic endometrium, often with p53 mutations and more aggressive behavior.
Clinical Manifestations
  • Abnormal Uterine Bleeding (AUB):
    • The most common symptom, particularly postmenopausal bleeding.
    • In premenopausal women, may present as irregular or heavy menstrual bleeding.
  • Pelvic Pain and Mass:
    • More common in advanced disease, often due to tumor growth.
  • Asymptomatic:
    • Early cases may be incidentally discovered.
Diagnosis
  • Transvaginal Ultrasound (TVUS):
    • Initial imaging for postmenopausal bleeding; endometrial thickness >4 mm in postmenopausal women is concerning.
  • Endometrial Biopsy:
    • Gold standard for diagnosis, providing histologic evaluation of the endometrium.
    • Recommended for any postmenopausal bleeding and for premenopausal women with high-risk factors and abnormal bleeding.
  • Hysteroscopy:
    • Allows visualization of the endometrial cavity and biopsy, especially useful for focal lesions.
Staging
  • FIGO Staging System:
    • Stage I: Confined to the uterus.
    • IA: Invasion limited to <50% of the myometrium.
    • IB: Invasion ≥50% of the myometrium.
    • Stage II: Involves cervical stroma.
    • Stage III: Spread to pelvic or para-aortic lymph nodes.
    • Stage IV: Extension to bladder, bowel, or distant organs.
Treatment
  • Surgical Management:
    • Total Hysterectomy with Bilateral Salpingo-Oophorectomy (THBSO) is the primary treatment, often with lymph node sampling.
  • Adjuvant Therapy:
    • Radiation Therapy: For high-risk or advanced-stage disease to reduce recurrence risk.
    • Chemotherapy: Used for high-grade, advanced, or type II cancers, with agents like carboplatin and paclitaxel.
  • Hormonal Therapy:
    • High-dose progestins or a levonorgestrel IUD may be used for estrogen receptor-positive tumors or in patients who desire fertility preservation.
Key Points
  • Endometrial Cancer is the most common gynecologic malignancy, usually presenting with postmenopausal bleeding.
  • Types:
    • Type I (endometrioid) is linked to estrogen exposure and endometrial hyperplasia.
    • Type II (non-endometrioid) is independent of estrogen and has a more aggressive course.
  • Risk Factors include unopposed estrogen exposure, obesity, nulliparity, PCOS, Lynch syndrome, and tamoxifen use.
  • Diagnosis:
    • Transvaginal ultrasound and endometrial biopsy are primary diagnostic tools.
  • Staging follows the FIGO system, assessing myometrial invasion and spread to lymph nodes or distant sites.
  • Treatment:
    • Surgery (THBSO) is standard; radiation and chemotherapy are used for advanced disease.
    • Hormonal therapy may be an option for select patients, especially for fertility preservation.

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