Karsinoma Ovarium

01Pathophysiology

Ovarian cancer develops through several distinct pathways depending on the histologic subtype. Understanding these pathways is essential because the exam frequently links the mechanism to the clinical behavior and treatment response of each type.

High-grade serous carcinoma (HGSC), which accounts for roughly 70% of epithelial ovarian cancers, is now understood to originate predominantly from the serous tubal intraepithelial carcinoma (STIC) in the distal fallopian tube fimbriae rather than from the ovarian surface. These cells harbor near-universal TP53 mutations and exhibit genomic instability. They implant onto the ovarian surface and disseminate rapidly into the peritoneal cavity through a process of transcoelomic spread. This explains why most patients present at an advanced stage with peritoneal carcinomatosis and ascites: malignant cells shed from the tube or ovary, circulate in the peritoneal fluid, and implant on the omentum, bowel serosa, diaphragm, and peritoneal surfaces. The accumulation of malignant ascites is driven by increased vascular permeability from tumor-secreted VEGF and obstruction of lymphatic drainage.

Low-grade serous carcinoma follows a different biology. It arises through a stepwise progression from serous cystadenoma to serous borderline tumor to invasive carcinoma, driven by KRAS or BRAF mutations rather than TP53. These tumors grow more indolently and are relatively chemoresistant.

Endometrioid and clear cell carcinomas are strongly associated with endometriosis. Ectopic endometrial tissue undergoes malignant transformation, often linked to mutations in ARID1A (a chromatin remodeling gene) and PIK3CA. Clear cell carcinoma is notorious for being chemoresistant and for its association with thromboembolic events and hypercalcemia.

Mucinous tumors arise either as primary ovarian neoplasms (driven by KRAS mutations) or, more commonly on the exam, as metastases from gastrointestinal primaries (the Krukenberg tumor, characterized by signet ring cells). This distinction is tested often: a bilateral mucinous tumor in a young woman should raise concern for a GI primary rather than a primary ovarian malignancy.

Germ cell tumors arise from primordial germ cells and are the most common ovarian malignancy in women under 30. These include dysgerminoma (the ovarian counterpart of testicular seminoma), yolk sac tumor (endodermal sinus tumor), and immature teratoma. Each produces characteristic tumor markers.

Sex cord-stromal tumors arise from the hormonally active cells of the ovary. Granulosa cell tumors produce estrogen, causing precocious puberty in children or postmenopausal bleeding in older women. Sertoli-Leydig cell tumors produce androgens, leading to virilization.

The reason ovarian cancer presents so late is fundamentally anatomic: the ovaries sit in the peritoneal cavity with no serosal barrier to contain early tumor spread, and the symptoms of peritoneal involvement (bloating, early satiety, vague abdominal pain) overlap extensively with benign conditions.

02Classification and Clinical Manifestation

by Histology

FIGO Staging

Early-stage disease (stages I and II) is frequently asymptomatic or produces only mild, nonspecific symptoms such as pelvic pressure or dyspareunia. The absence of a reliable screening tool for the general population means that only about 20% of ovarian cancers are caught at an early stage.

Advanced-stage disease (stages III and IV) produces the classic constellation of progressive abdominal distension from ascites, bloating, early satiety (from omental caking compressing the stomach), changes in bowel habits, and pelvic pain. Right-sided pleural effusion is common due to transdiaphragmatic lymphatic channels that allow peritoneal fluid to track into the thorax. A patient presenting with a new right-sided pleural effusion, ascites, and a pelvic mass is a classic vignette construction.

03Diagnostic Workup

When a vignette describes a postmenopausal woman with bloating, increasing abdominal girth, and a pelvic mass, the first step is a transvaginal ultrasound. This is the best initial test to characterize the adnexal mass. Features that raise suspicion for malignancy include solid components, thick septations, papillary excrescences, and bilateral involvement. A simple, thin-walled, unilocular cyst in a premenopausal woman is almost always benign and can be observed.

CA-125 should be obtained simultaneously. In postmenopausal women, an elevated CA-125 combined with a suspicious mass on ultrasound has strong positive predictive value for epithelial ovarian cancer. However, in premenopausal women, CA-125 has poor specificity because it is elevated in a wide range of benign conditions including endometriosis, pelvic inflammatory disease, uterine fibroids, pregnancy, and even menstruation. This is a commonly tested concept.

If malignancy is suspected based on imaging and markers, CT of the chest, abdomen, and pelvis is performed for staging and to evaluate for peritoneal disease burden, omental involvement, and lymphadenopathy. This guides surgical planning and helps determine whether optimal debulking is feasible.

The gold standard for diagnosis is histopathologic examination of tissue obtained at surgery. A critical exam point: suspected ovarian cancer should not be biopsied percutaneously (via fine-needle aspiration or core biopsy) because of the risk of tumor seeding along the needle tract and peritoneal spillage. The appropriate approach is surgical excision and staging, not needle biopsy.

For younger women with suspected germ cell tumors, the marker panel shifts to AFP, beta-hCG, and LDH. Elevated AFP points to a yolk sac tumor, elevated beta-hCG points to choriocarcinoma or mixed germ cell tumor, and elevated LDH points to dysgerminoma.

There is no recommended routine screening for ovarian cancer in the general population. Neither CA-125 nor transvaginal ultrasound has been shown to reduce mortality when used for screening in average-risk women. However, women with known BRCA1 or BRCA2 mutations should be counseled about risk-reducing bilateral salpingo-oophorectomy (RRBSO), ideally between ages 35 and 40 for BRCA1 and 40 and 45 for BRCA2, after completion of childbearing.

04Management and Treatment

The cornerstone of ovarian cancer treatment is surgery first, then chemotherapy, unless the disease burden precludes optimal resection.

Surgical staging is critical and must be comprehensive. For a patient who undergoes removal of an adnexal mass and is found to have ovarian cancer on pathology, the question will test whether you know that the patient needs to go back for completion staging surgery (hysterectomy, contralateral oophorectomy, omentectomy, lymph node sampling, peritoneal biopsies) if staging was not performed at the initial operation. This is a commonly tested "next best step."

Optimal cytoreduction means reducing all visible disease to residual nodules of less than 1 cm. The amount of residual disease after surgery is the single strongest prognostic factor for survival in advanced-stage ovarian cancer. If the surgeon determines preoperatively that optimal debulking is not achievable, the patient should receive neoadjuvant chemotherapy (3 cycles of carboplatin + paclitaxel) to shrink the tumor burden, followed by interval debulking surgery, followed by 3 more cycles of chemotherapy.

The standard chemotherapy regimen is carboplatin (dosed by AUC, typically 5 to 6) plus paclitaxel (175 mg/m${}^2^\{2\}$), administered intravenously every 21 days for 6 cycles. Dose-dense weekly paclitaxel (80 mg/m${}^2^\{2\}$) is an alternative schedule that may offer a survival advantage in certain populations.

PARP inhibitors (olaparib, niraparib) represent the most tested pharmacologic advance. These drugs exploit the concept of synthetic lethality: tumor cells with BRCA mutations already have defective homologous recombination repair, and when PARP (another DNA repair pathway) is also blocked, the accumulation of DNA damage causes tumor cell death. Vignettes may describe a patient with a BRCA mutation whose cancer has responded to platinum chemotherapy and then ask about the best maintenance therapy. The answer is a PARP inhibitor.

For germ cell tumors, the approach is different. Fertility-sparing surgery (unilateral salpingo-oophorectomy) is standard because these tumors affect young women and are highly chemosensitive. Adjuvant BEP (bleomycin, etoposide, cisplatin) chemotherapy is given for all stages beyond stage IA. Cure rates exceed 90% even for advanced-stage disease.

05Differential Diagnosis and Distractors

06Traps and High-Yield Pearls

The most frequent way students lose points on ovarian cancer questions is by confusing the role of CA-125 in premenopausal versus postmenopausal women. The exam loves to present a premenopausal woman with a mildly elevated CA-125 and a simple-appearing ovarian cyst. Students panic and choose surgical intervention, but the correct answer is observation (or repeat imaging in 6 to 8 weeks) because CA-125 is unreliable in this age group. In contrast, the same CA-125 level in a postmenopausal woman with a complex adnexal mass demands surgical evaluation.

Another classic trap is presenting a patient with ovarian cancer found incidentally during a simple cystectomy and then asking for the next step. Students choose chemotherapy, but the correct answer is return to the operating room for comprehensive surgical staging, because the initial surgery was inadequate.

Students also confuse Meigs syndrome with advanced ovarian cancer. Both present with a pelvic mass, ascites, and pleural effusion. The distinguishing feature is that Meigs syndrome involves a benign fibroma, and the effusion and ascites resolve after the tumor is removed. A vignette that emphasizes a solid ovarian mass without peritoneal implants and then asks about prognosis after resection is hinting at Meigs.

The concept of BRCA testing and PARP inhibitors is increasingly tested. Students should recognize that all patients with epithelial ovarian cancer (particularly high-grade serous) should undergo germline and somatic BRCA testing at diagnosis, because the result changes maintenance therapy. If the vignette mentions a positive BRCA mutation and a platinum-sensitive recurrence or initial response, the next step in management after completing chemotherapy is a PARP inhibitor.

Finally, remember the germ cell tumor markers. A young woman with a solid ovarian mass and elevated AFP has a yolk sac tumor until proven otherwise, and the treatment is fertility-sparing surgery plus BEP chemotherapy, not a total hysterectomy. The exam tests whether you preserve fertility in this population.

The core competency being tested across ovarian cancer questions is your ability to match the patient demographics and tumor markers to the correct histologic subtype, select the appropriate diagnostic pathway (never percutaneous biopsy), and understand that the sequence of surgery and chemotherapy depends on whether optimal cytoreduction is achievable.