Invasive breast carcinoma - IARC

mixed Brenner-mucinous cystic tumour,
both components should be macroscopically
visible. A mixed epithelial tumour
(MET) may be benign, borderline or
malignant. Endometrioid tumours with
squamous differentiation and neuroendocrine
tumours associated with a surface
epithelial-stromal tumour are not
included in this definition.
ICD-O codes
Malignant mixed epithelial tumour 8323/3
B o rderline mixed epithelial tumour 8323/1
Benign mixed epithelial tumour 8323/0
A
Epidemiology
The reported incidence of MET varies
from 0.5-4% of surface epithelial-stromal
tumours. This variability is due in part to
problems in developing a standardized
classification.
Tumour spread and staging
Mixed epithelial borderline tumours
(MEBTs) are stage I in 93% of cases and
show bilateral ovarian involvement in
22% {2496}.
B
Fig. 2.54 Undifferentiated carcinoma of the ovary. A Sheets of tumour cells with small cystic spaces are
separated by irregular fibrous septa. B Aggregates of undifferentiated tumour cells with pleomorphic nuclei
and frequent mitotic figures are separated by thin bands of fibrous stroma.
squamous cell carcinomas have
occurred in women with cervical squamous
cell carcinoma in situ {1738}.
Prognosis and predictive factors
Most tumours have spread beyond the
ovary at the time of presentation, and the
prognosis in the small number of reported
cases is poor.
Epidermoid cyst
Definition
Benign ovarian cysts lined by squamous
epithelial cells that are not clearly of
germ cell origin.
Histopathology
Epidermoid cysts lined by benign keratinized
squamous epithelium devoid of
skin appendages and unaccompanied
by teratomatous elements are rare in the
ovary {823,3205}. All are small (2-46 mm)
and unilateral.
Histogenesis
The presence of small epithelial cell
nests resembling Walthard cell nests in
the walls of epidermoid cysts suggests
an epithelial rather than a teratomatous
origin {3205}.
Mixed epithelial tumours
Definition
An ovarian epithelial tumour composed
of an admixture of two or more of the five
major cell types: serous, mucinous,
endometrioid, clear cell and
Brenner/transitional. The second or second
and third cell types must comprise
alone or together at least 10% of the
tumour epithelium, or, in the case of a
Histopathology
In cystadenomas the most frequent mixture
is serous (ciliated) and mucinous
epithelium. The mucinous epithelium
should contain abundant intracytoplasmic
mucin, not just apical or luminal
mucin. MEBTs show papillae with
detached cell clusters reminiscent of
serous borderline tumours, but they generally
contain a mixture of endocervicallike
mucinous cells, endometrioid epithelium
with focal squamous differentiation
and indifferent eosinophilic epithelium.
An acute inflammatory infiltrate is frequently
seen. Microinvasion may be
seen rare l y. Mixed Bre n n e r- m u c i n o u s
tumours are usually composed of a
benign, and, occasionally, a borderline
Brenner component; the mucinous component
may be benign, borderline or
malignant. A few mucinous glands within
Brenner nests or histological areas of
mucinous differentiation represent mucinous
metaplasia in Brenner tumours, a
common finding, and are not a MET.
Rarely, the tumour macroscopically contains
a myriad of small cysts lined by an
admixture of mucinous and transitional
epithelium and the term metaplastic
Brenner tumour is applied {2461}. For
c y s t a d e n o c a rcinomas frequent combinations
are serous and endometrioid,
144 Tumours of the ovary and peritoneum