STEPTRACKERREPRODUCTIVE + ONCOLOGY | PATHOLOGY + GENETICS | HIGH-YIELD REVIEW

Ovarian Epithelial Tumors

The most common ovarian tumors — serous, mucinous, endometrioid, clear cell and Brenner — and why they are found late.

FOCUS ON
Epithelial tumors are the most common ovarian tumors, mostly in postmenopausal women. High-grade serous carcinoma (most common malignant): TP53, BRCA, starts in the fallopian tube, psammoma bodies, spreads over the peritoneum. Risk ↑ with ovulation count, BRCA, Lynch, endometriosis; ↓ with OCPs, pregnancy, breastfeeding. CA-125 monitors, doesn't screen.
TUMOR · TOPIC
MECHANISM · GENETICS
FEATURES
CLUE
Presentation
Silent growth; peritoneal spread before symptoms
Bloating, early satiety, pelvic pressure, ascites, omental caking
Late diagnosis → poor survival
Serous cystadenoma
Benign; tubal-type ciliated epithelium
Thin-walled cyst with clear fluid; may be bilateral
Most common benign epithelial tumor
Serous borderline / low-grade carcinoma
KRAS, BRAF; stepwise from cystadenoma
Papillary growth without (borderline) or with invasion
Slow-growing, younger patients
High-grade serous carcinoma
most common malignant
TP53; BRCA1/2; arises from serous tubal intraepithelial carcinoma in the fimbriae
Bilateral, solid-cystic; papillae, psammoma bodies; WT1, PAX8 ⁺; peritoneal spread
↑ CA-125 · PARP inhibitors in BRCA
Mucinous cystadenoma
Benign; endocervical or intestinal-type mucinous epithelium
Very large, multiloculated cyst with sticky mucin; usually unilateral
Smoking association
Mucinous carcinoma
KRAS; often unilateral
Must exclude metastasis from GI tract (bilateral, small = likely metastatic)
Pseudomyxoma peritonei usually from appendix
Endometrioid carcinoma
From endometriosis; PTEN, ARID1A, CTNNB1
Glands resembling endometrium; may coexist with endometrial carcinoma
Lynch syndrome
Clear cell carcinoma
From endometriosis; ARID1A
Clear glycogen-rich cells, hobnail cells
Paraneoplastic hypercalcemia, thrombosis
Brenner tumor
Urothelial (transitional)-like nests in fibrous stroma
Usually benign, solid, unilateral; "coffee bean" nuclei
Incidental in older women
Hereditary risk
BRCA1 > BRCA2; Lynch (MMR)
Earlier-onset high-grade serous (BRCA) or endometrioid/clear cell (Lynch)
Risk-reducing salpingo-oophorectomy
Spread & markers
Exfoliation onto peritoneum; lymphatics (para-aortic)
Ascites, peritoneal implants, bowel obstruction; pleural effusion
CA-125 ↑ also in endometriosis, PID, pregnancy

Mechanism — two models of ovarian carcinogenesis

Fallopian tube fimbria
→
TP53 signature → STIC
→
Seeds ovary + peritoneum
→
High-grade serousFast, aggressive
Benign / borderline tumor or endometriosis
→
KRAS, BRAF, ARID1A, PTEN
→
Low-grade serous, mucinous, endometrioid, clear cellSlower

Every ovulation injures and repairs epithelium; fewer ovulations (OCPs, pregnancy, breastfeeding) lower risk.

Risk and protection

↑ RISK
↓ RISK
BRCA1/2, Lynch syndrome
Combined oral contraceptives
Nulliparity, infertility
Pregnancy, multiparity
Early menarche, late menopause
Breastfeeding
Endometriosis (endometrioid, clear cell)
Tubal ligation, salpingectomy
Smoking (mucinous), older age
Hysterectomy

How it's tested

COMMON CONFUSIONPsammoma bodies appear in serous ovarian carcinoma, papillary thyroid carcinoma, meningioma and mesothelioma. In a woman with ascites and an adnexal mass, think serous carcinoma.
THE TRAPCA-125 is not a screening test for average-risk women — it rises with many benign conditions. Use it to monitor treatment and recurrence.
YOUR APPROACHPatient (age, BRCA/Lynch, endometriosis) → cyst vs solid, uni vs bilateral → histologic type → marker → spread pattern.

If you see… think…

Postmenopausal woman, bloating, ascites, omental caking, ↑ CA-125 → high-grade serous carcinoma
Ovarian carcinoma in a BRCA1 carrier → high-grade serous
Precursor lesion for high-grade serous carcinoma → STIC in the fallopian tube
Huge multiloculated cyst full of sticky mucin → mucinous cystadenoma
Bilateral small mucinous ovarian tumors → metastasis from GI tract
Ovarian tumor with hobnail cells in a woman with endometriosis → clear cell carcinoma
Synchronous endometrial and ovarian endometrioid cancers → Lynch syndrome
Solid tumor with urothelial-like nests, coffee bean nuclei → Brenner tumor
Strongest protective factor you can prescribe → combined OCPs
Treatment that exploits BRCA-deficient DNA repair → PARP inhibitor (olaparib)