Endometrioid, clear cell and Brenner tumours of the ovary
- Lesion
Two ovarian cancers that grow out of endometriosis, and a mostly benign tumour made of cells that look like bladder lining.
What it is
Endometrioid and clear cell carcinomas of the ovary are the endometriosis-associated cancers. Endometrioid carcinoma resembles its endometrial namesake, shares mutations in PTEN, ARID1A, CTNNB1 and the mismatch repair genes, and may coexist with an independent-looking endometrial carcinoma. Clear cell carcinoma has glycogen-rich clear and hobnail cells, ARID1A loss and resistance to chemotherapy. Brenner tumours are usually small, benign, solid tumours of urothelial-like nests in fibrous stroma.
Structure
- Endometrioid: solid and cystic mass, back-to-back glands with columnar cells, squamous differentiation.
- Clear cell: cells with abundant clear cytoplasm (glycogen) and hobnail nuclei, hyaline basement-membrane material in papillae.
- Brenner: a firm white nodule; urothelial-type nests, sometimes with central mucinous cells; Walthard cell nests on the tube may be their origin.
Step by step
- Endometriosis on the ovary provides epithelium under chronic oxidative stress from repeated haemorrhage.
- ARID1A, PIK3CA and other mutations accumulate in the endometriotic epithelium.
- Atypical endometriosis develops, then invasive endometrioid or clear cell carcinoma.
- Mismatch-repair defects, sporadic or from Lynch syndrome, contribute in a subset.
Markers
- PAX8 positive
- ER and PR (endometrioid)
- Napsin A and HNF1-beta (clear cell)
- GATA3 and p63 (Brenner)
Clinical notes
- Often present at an earlier stage than high-grade serous carcinoma, as a pelvic mass in a woman with endometriosis.
- Ovarian clear cell carcinoma is associated with hypercalcaemia and thromboembolism.
- Patients with endometrioid or clear cell carcinoma are tested for mismatch-repair deficiency.
Test yourself
Think of the answer, then tap the question to see it.
Which two ovarian carcinomas arise from endometriosis?
Endometrioid carcinoma and clear cell carcinoma.
Which gene is commonly lost in both?
ARID1A, a chromatin-remodelling tumour suppressor.
What does a Brenner tumour look like under the microscope?
Nests of urothelial-like (transitional) cells with grooved coffee-bean nuclei in a dense fibrous stroma.
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Connections
Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.
Sources: Epithelial Ovarian Cancer (StatPearls (NCBI Bookshelf), 2026); Endometriosis (StatPearls (NCBI Bookshelf), 2026).
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Representative model, for educational purposes only.