Low-grade serous ovarian tumours
- Lesion
Serous tumours that grow slowly: from a harmless cyst to a borderline tumour and, rarely, a low-grade cancer, driven by KRAS or BRAF rather than TP53.
What it is
Serous tumours are built of cells like those lining the fallopian tube. On the low-grade pathway, a benign serous cystadenoma or cystadenofibroma can give rise to a serous borderline tumour, which proliferates in branching papillae without invading, and some borderline tumours progress to low-grade serous carcinoma. These tumours carry KRAS, BRAF or ERBB2 mutations, keep wild-type TP53, grow slowly and respond poorly to chemotherapy. They are a different disease from high-grade serous carcinoma.
Structure
- Benign: thin fibrous wall, a single layer of columnar ciliated cells, sometimes a fibrous stromal component (cystadenofibroma).
- Borderline: papillary excrescences on the inner or outer surface of the cyst; layered cells budding off in tufts.
- Micropapillary variant of borderline tumour: long slender papillae without branching, closer to carcinoma.
- Low-grade carcinoma: invasive small nests and micropapillae in retraction spaces, low mitotic rate.
Step by step
- Tubal-type epithelium on the ovarian surface or in cortical inclusion cysts forms a benign serous cyst.
- A KRAS, BRAF or ERBB2 mutation lets a clone proliferate into papillae (borderline tumour).
- Additional changes in a minority allow destructive invasion (low-grade serous carcinoma).
- Spread is mostly along peritoneal surfaces; growth is slow over years.
Low-grade vs high-grade serous carcinoma
| Feature | Low-grade serous carcinoma | High-grade serous carcinoma |
|---|---|---|
| Precursor | Cystadenoma and borderline tumour | Serous tubal intraepithelial carcinoma |
| Key genes | KRAS, BRAF, ERBB2; TP53 normal | TP53 in nearly all; BRCA1 or BRCA2 in a share |
| Nuclei | Uniform, mild atypia | Marked atypia, many mitoses |
| Age and course | Younger, slow growth | Older, rapid spread |
| Chemotherapy | Responds poorly | Responds initially, often relapses |
Markers
- PAX8 and WT1 positive
- p53 wild-type pattern
- Psammoma bodies (calcification)
Clinical notes
- Present as an adnexal mass or are found on imaging; borderline tumours occur in younger women and can be treated with fertility-sparing surgery.
- CA-125 may be raised but is not specific.
Test yourself
Think of the answer, then tap the question to see it.
What separates a serous borderline tumour from carcinoma?
The absence of destructive stromal invasion despite papillary proliferation and atypia.
Which genes drive low-grade serous tumours?
KRAS, BRAF or ERBB2, with wild-type TP53.
What is a psammoma body?
A laminated concretion of dystrophic calcium, typical of papillary tumours such as serous ovarian tumours.
Elsewhere in DurgiPedia
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); Ovarian Epithelial, Fallopian Tube, and Primary Peritoneal Cancer Treatment (PDQ®)–Health Professional Version (National Cancer Institute, 2026).
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Representative model, for educational purposes only.