Karsinoma Endometrium

01Pathophysiology

Endometrial cancer is fundamentally a disease of estrogen-progesterone imbalance. The endometrium is an estrogen-responsive tissue. Under normal physiology, estrogen stimulates endometrial proliferation during the follicular phase, and progesterone secreted after ovulation counteracts this by inducing secretory differentiation and stabilizing the endometrium. When progesterone is absent or insufficient, estrogen drives continuous, unchecked proliferation, which over time leads to endometrial hyperplasia and eventually malignant transformation.

This is the mechanistic basis for understanding why every major risk factor converges on the same theme: excess estrogen without progesterone opposition. Obesity is the most important modifiable risk factor because adipose tissue contains aromatase, which converts adrenal androgens into estrone (a peripheral estrogen source). The more adipose tissue, the higher the circulating estrogen. Anovulatory states such as PCOS remove the progesterone counterbalance entirely because no corpus luteum forms. Tamoxifen, while acting as an estrogen antagonist in breast tissue, behaves as a partial estrogen agonist in the endometrium, which is why breast cancer patients on tamoxifen carry increased endometrial cancer risk and require monitoring for abnormal bleeding.

Type I endometrial cancer (endometrioid adenocarcinoma) accounts for roughly 80% of cases. It follows the estrogen-driven pathway described above, tends to be low grade, is preceded by hyperplasia, and generally carries a favorable prognosis because it presents early with bleeding.

Type II endometrial cancer (serous papillary and clear cell carcinoma) is fundamentally different. It is not estrogen-dependent, arises from atrophic endometrium in older, thinner women, behaves aggressively, and is often diagnosed at an advanced stage. Type II tumors frequently harbor p53 mutations and carry a significantly worse prognosis. The test-writer uses this distinction to assess whether students understand that not all endometrial cancers are driven by estrogen excess.

Lynch syndrome (formerly known as hereditary nonpolyposis colorectal cancer) deserves special mention. It is caused by germline mutations in DNA mismatch repair genes (MLH1, MSH2, MSH6, PMS2). After colorectal cancer, endometrial cancer is the second most common malignancy in Lynch syndrome, with a lifetime risk of 40-60%. A young woman presenting with endometrial cancer and a family history of colon, ovarian, or endometrial cancer should raise suspicion for this syndrome.

02Classification and Clinical Manifestation

Histologic Classification

FIGO Staging

Endometrial Hyperplasia Classification

The presence of cytologic atypia is the single most important histologic feature that determines cancer risk. This distinction is heavily tested.

Clinical Manifestation by Stage

03Diagnostic Workup

Summary Table

The diagnostic sequence on the exam almost always begins with a postmenopausal woman presenting with vaginal bleeding. The best initial step is transvaginal ultrasound to measure endometrial stripe thickness. The threshold of >4 mm in a postmenopausal woman is the number to remember. If the stripe is thickened or the patient has persistent bleeding regardless of stripe thickness, the next step is tissue sampling.

Endometrial biopsy (Pipelle sampling) is the standard office-based procedure and is the best initial tissue diagnostic test. It has a sensitivity of approximately 90-95% for detecting endometrial cancer. However, it is a blind sampling technique, meaning it can miss focal lesions. If the Pipelle biopsy returns as insufficient tissue, nondiagnostic, or discordant with clinical suspicion, the next step is dilation and curettage, ideally with hysteroscopy for direct visualization.

A common exam scenario involves a postmenopausal woman on tamoxifen who develops vaginal bleeding. The workup is the same: TVUS first, then biopsy. Do not simply attribute the bleeding to tamoxifen without ruling out malignancy.

Preoperative staging with pelvic MRI is used to evaluate the depth of myometrial invasion, which directly impacts surgical planning and the decision to perform lymph node dissection. CT imaging is reserved for evaluating distant spread in advanced-stage disease or aggressive histologic subtypes like serous carcinoma.

One important caveat: endometrial cancer is surgically staged, not clinically staged. The final FIGO stage is determined at the time of surgery, not by imaging alone. This is a testable concept.

04Management and Treatment

Summary Table

Total abdominal hysterectomy with bilateral salpingo-oophorectomy (TAH-BSO) is the cornerstone of treatment for endometrial cancer. The ovaries are removed because they are a source of estrogen, and occult metastasis to the adnexa may be present. Surgical staging includes peritoneal washings, pelvic and para-aortic lymph node assessment, and inspection of all peritoneal surfaces.

For early-stage, low-grade disease (Stage IA, Grade 1-2), surgery alone is curative in the vast majority of patients, and adjuvant therapy is not indicated. This is a testable point because examinees may reflexively add radiation.

For higher-risk early-stage disease (Stage IA Grade 3, Stage IB, or Stage II), adjuvant vaginal cuff brachytherapy reduces local recurrence at the vaginal cuff, which is the most common site of recurrence. External beam pelvic radiation is added when lymph node involvement is present or suspected.

For advanced-stage disease (Stage III-IV), the standard systemic chemotherapy regimen is carboplatin (AUC 5-6) + paclitaxel (175 mg/m${}^2^2$), administered every 3 weeks for 6 cycles. This is the same backbone regimen used for ovarian cancer and is high-yield to know.

Type II tumors (serous and clear cell) are managed aggressively regardless of stage. Even Stage IA serous carcinoma requires comprehensive surgical staging including omentectomy and peritoneal biopsies, followed by adjuvant chemotherapy, because of the high propensity for peritoneal spread (similar to ovarian cancer behavior).

For the young patient with atypical hyperplasia or early Grade 1 endometrioid cancer who desires fertility preservation, continuous progestin therapy is an acceptable temporizing approach. Options include oral medroxyprogesterone acetate, megestrol acetate, or a levonorgestrel-releasing intrauterine device. These patients must undergo repeat endometrial sampling every 3 to 6 months to confirm regression, and definitive hysterectomy is strongly recommended once childbearing is complete.

Molecular profiling has become increasingly relevant. Tumors with microsatellite instability-high (MSI-H) or deficient mismatch repair (dMMR) status respond to immune checkpoint inhibitors such as pembrolizumab, particularly in the recurrent or advanced setting. The combination of pembrolizumab + lenvatinib is used for advanced endometrial cancer that is microsatellite stable (MSS) and has progressed on prior chemotherapy.

05Differential Diagnosis and Distractors

06Traps and High-Yield Pearls

The single most common trap on this topic is the student who sees postmenopausal bleeding and jumps directly to endometrial biopsy without first ordering a transvaginal ultrasound. While biopsy is the tissue diagnostic test, the best initial step in a stable postmenopausal patient with vaginal bleeding is TVUS. The ultrasound serves as a triage tool: if the endometrial stripe is less than or equal to 4 mm, the negative predictive value for cancer is greater than 99%, and biopsy can be deferred with clinical follow-up. If the stripe is thickened, biopsy follows.

Another frequently tested trap is the tamoxifen patient. Students see a thickened endometrial stripe on routine imaging and want to biopsy. The key principle is: do not biopsy an asymptomatic tamoxifen patient based on ultrasound findings alone, because tamoxifen causes subendometrial cystic changes that artificially inflate the measured thickness. Biopsy is indicated only when there is abnormal bleeding.

Students also confuse atypical hyperplasia with cancer. The distinction matters enormously for management: atypical hyperplasia can be treated with progestins in a young patient desiring fertility, whereas invasive cancer generally requires hysterectomy. However, up to 40% of patients with atypical hyperplasia on biopsy are found to have concurrent invasive carcinoma in the hysterectomy specimen, which is why hysterectomy remains the definitive recommendation when fertility is not a concern.

The Type I vs. Type II distinction is another area where students lose points. A thin, elderly postmenopausal woman with aggressive-appearing endometrial cancer does not fit the "classic" estrogen-excess profile, and that mismatch itself is a clue that you are dealing with a Type II (serous or clear cell) tumor, which requires more aggressive staging and treatment.

Finally, remember that endometrial cancer is surgically staged. A question stem that provides imaging results and asks for the "stage" is testing whether you know that final staging requires pathologic evaluation of the surgical specimen, not imaging alone. The correct answer in such a scenario is to proceed with surgery, not to assign a clinical stage based on MRI or CT findings.