Invasive breast carcinoma - IARC

origin, the mitochondrial DNA is of
m a t e rnal origin {146}.
Partial hydatidiform mole
Definition
A hydatidiform mole having two populations
of chorionic villi, one of normal size
and the other hydropic, with focal trophoblastic
proliferation. The lesion typically
has a triploid karyotype.
Fig. 4.52 “Early” complete mole. Some villi have
toe-like bulbous protrusions. Trophoblastic proliferation
and cavitation are minimal. The stroma is
hypercellular and myxoid.
Fig. 4.54 Markedly atypical implantation site trophoblast
in a case of early hydatidiform mole.
Fig. 4.51 MRI of hydatidiform mole adjacent to a
normal fetus in a twin pregnancy.
Histopathology
Histologically, partial moles are characterized
by the concurrence of four feat
u res {977,1319,1593,2170,2348,2365,
2828,2829}:
(1) Two populations of villi, one hydropic
and one "normal";
(2) Minimal trophoblastic hyperplasia
involving syncytiotrophoblast.
(3) Enlarged cavitated villi.
(4) Other villi with scalloped borders,
often containing trophoblastic inclusions.
S t romal blood vessels often contain
nucleated fetal red blood cells; other evidence
suggesting fetal development is
common, including portions of the chorionic
sac wall, amnion, umbilical cord and
embryonic/fetal tissue.
The diff e rential diagnosis of partial hydat
i d i f o rm mole includes:
(1) Complete mole.
(2) Hydropic abort u s .
(3) Several rare sporadic genetic synd
romes with focal placental hydrops and
a fetus, such as the Beckwith-
Weidemann syndrome {1558} and placental
angiomatous malformation {2522},
which collectively have been termed "placental
mesenchymal dysplasia" {1337}.
In instances in which the histological
diagnosis is uncertain, cytogenetic
Fig. 4.53 Partial hydatidiform mole. There are two
populations of villi; the larger is markedly irregular
with scattered cavitation, numerous trophoblastic
inclusions and minimal hyperplasia.
Fig. 4.55 Placental site nodule. Note the well circumscribed
eosinophilic endomyometrial nodules.
analysis or flow cytometry may be of
assistance {549,882,933,1485,1557-
1563,2170}.
Somatic genetics
In contrast to complete moles, part i a l
moles generally have a triploid kary o t y p e
that results from fertilization of an apparently
normal ovum by two sperm {2828}.
The re p o rted incidence of triploidy in partial
moles varies from 90-93% re s p e c t i v e l y
{1560,1593}. When fetuses are identified
with partial moles, they usually have stigmata
of triploidy including multiple congenital
anomalies and growth re t a rd a t i o n .
Invasive hydatidiform mole
Definition
Invasive hydatidiform mole is defined as
villi of hydatidiform mole within the
myometrium or its vascular spaces.
Histopathology
Most invasive moles follow complete
hydatidiform mole and have the characteristic
histological appearance of that
lesion. Rare examples of invasive partial
mole have also been described {33,
942,1065,2841,3131}. A hysterectomy is
usually required for the histological diagnosis.
Metastatic hydatidiform mole
Definition
Metastatic hydatidiform mole is defined
as extrauterine molar villi within blood
vessels or tissues, most commonly the
vagina or the lung.
Non-neoplastic, non-molar
trophoblastic lesions
Placental site nodule or plaque
The placental site nodule or plaque
{1260,3203} is a well circumscribed lesion
with abundant hyalinized stroma infiltrated
by scattered, degenerated-appearing
i n t e rmediate trophoblastic cells; these
cells show no significant cytological atypia,
but rare mitoses may be present.
Exaggerated placental site
The exaggerated implantation site represents
a non-neoplastic exaggeration of
the normal implantation process, usually
found concurrently with immature villi.
254 Tumours of the uterine corpus