Low-Grade Serous Carcinoma
Epidemiology and Etiology:
- < 5% of all ovarian carcinomas
- Most likely represent progression of serous
borderline tumours beyond microinvasion
- Rarely progress to HG
Common sites:
Gross features:
- Frequently presents with bulky peritoneal
disease
Histologic features:
- infiltration of underlying stroma (invasive foci
> 10 mm2 by definition)
- disorderly architecture of glands
- desmoplastic stromal response is typical
- myxoid or hyaline stromal response occasionally
- not limited to surfaces of polypoid
excrescences (“auto-implantation”)
- architectural features variety:
- micropapillae
- (note: not sufficient by itself to warrant a
diagnosis of carcinoma in the absence of invasion)
- micropapillary projections like medusae
- macropapillae less common
- irregularly shaped small, tight nests with
haphazard infiltration of stroma
- glomeruloid formations
- single cells
- uniform nuclei is principal criterion for
distinguishing from high-grade
- mild to moderate nuclear atypia
- < 3-fold variability in size
- Single prominent nucleolus maybe
- Mitotic activity is significantly lower than
HGSC (usually < 2-3 mitotic figures per 10 HPF)
- Intermediate size nuclei often associates with
TP53 mutations and should be classified as HG
- frequently non-invasive serous borderline
component (with or without micropapillary
pattern)
- psammoma
bodies often within hyalinized stroma
- almost never necrosis
-
Immunophenotype:
|
Marker:
|
Sensitivity:
|
Specificity:
|
|
CK7
|
|
|
|
WT1
|
|
|
|
Ki-67 (2.5 %
median)
|
|
22.4% median in
HGSC
|
|
PR
|
50%
|
Higher percentage
of borderline tumours are positive
|
|
p53
(normal
staining pattern)
|
|
Can be useful in
distinction from HGSC
|
- Identical
to serous borderline tumour/APST except for
lower PR expression (50%) of cases
Molecular features:
- BRAF mutation (38%)
- KRAS mutation (19%)
- Lack of chromosomal instability
- Lack of complex genetic abnormalities
- Lack of BRCA germline mutations
Other features:
- Indolent course
- Presence of small foci of LGSC in an ovarian
borderline tumour is associated with an
excellent prognosis
- Advanced stage disease fare less favorably
- Poor response to conventional ovarian carcinoma
chemotherapy (early data)
References:
- Prat J.
Ovarian carcinomas: five distinct diseases with different origins,
genetic alterations, and clinicopathological
features. Virchows
Arch (2012) 460:237-249.
- Kurman
RJ, Carcangiu ML, Herrington CS, Young RH (eds.) WHO
Classification of Tumours of Female
Reproductive Organs. (2014)