Invasive breast carcinoma - IARC

ation may coexist in the same neoplasm,
their behaviour, with some exceptions
{1500}, is not conditioned by specific
tumour morphology but shows a generally
favourable response to chemotherapy.
Although the histological appearance
bears little prognostic implications,
mature or well differentiated glandular
forms may have an indolent course even
when treated by surgery alone {1500,
2284}.
Embryonal carcinoma and
polyembryoma
A
Fig. 2.93 A Yolk sac tumour. Note the polyvesicular vitelline area with biphasic lining. B Allantoic remnants
from an aborted embryo. The allantoic remnants from an aborted embryo are identical to the polyvesicular
vitelline structure shown in A.
B
Definition
Embryonal carcinoma is a tumour composed
of epithelial cells re s e m b l i n g
those of the embryonic disc and growing
in one or more of several patterns, gland
u l a r, tubular, papillary and solid.
Polyembryoma is a rare tumour composed
predomininantly of embryoid bodies
resembling early embryos.
Epidemiology
These rare tumours are the ovarian counterparts
of their more frequent testicular
homologues. Many are reported as a
component of mixed germ cell tumours
that originate from gonadoblastoma (see
section on mixed germ cell-sex cord
stromal tumours), arising in Y-chromosome
containing dysgenetic gonads
(and thus are technically "testicular"
tumours) or even in 46 XX gonads
{3253}. They are multipotent stem cell
tumours reproducing the primitive stages
of embryonal differentiation.
Clinical features
Clinically, β-hCG stimulation may determine
various hormonal manifestations
such as precocious pseudopuberty in
premenarchal girls and vaginal bleeding
in adult women {1536}.
Fig. 2.94 Embryonal carcinoma. Cells with primitive-appearing nuclei form solid aggregates and line irregular
gland-like spaces.
Histopathology
H i s t o l o g i c a l l y, embryonal carc i n o m a
reveals disorganized sheets of large
primitive AFP and CD30-positive cells
{736,1536}, forming papillae or crevices
which coexist with β-hCG positive syncytiotrophoblasts
as well as early teratoid
differentiation such as squamous, columnar,
mucinous or ciliated epithelia. Its
even more infrequent organoid variant is
called polyembryoma due to a structural
organization into blastocyst-like formations
that resemble early pre s o m a t i c
e m b ryos. These so-called embry o i d
bodies show embryonic disks with corresponding
amniotic or primary yolk sac
cavities and are surrounded by a
mesoblast-like loose connective tissue.
The surrounding tissues can differentiate
into endodermal structures such as
intestine or liver {2287} and trophoblast.
However close the resemblance to normal
early structures, the sequences of
early embryonal development are not
reproduced {1969}.
Non-gestational choriocarcinoma
A
B
Fig. 2.95 Embryonal carcinoma. A Numerous syncytiotrophoblastic giant cells are typical. B The tumour
cells show membranous staining for placental-like alkaline phosphatase.
Definition
A rare germ cell tumour composed of
cytotrophoblast, syncytiotrophoblast and
extravillous trophoblast.
Germ cell tumours 167