Invasive breast carcinoma - IARC

A
Fig. 4.49 A Classic complete hydatidiform mole. Note the dilated chorionic villi with the typical “bunch of grapes” appearance. B This molar villus is cavitated with
circumferential trophoblastic hyperplasia and atypia.
B
chorionic villi and typically having a
diploid karyotype.
Histopathology
The villous hydrops of a complete mole
is characterized by extensive cavitation.
The trophoblastic proliferation differs
from normal villi by its circ u m f e re n-
tial distribution, hyperplasia and cytological
atypia {978,1203}. Interm e d i a t e
t rophoblast of the molar implantation
site characteristically displays marked
cytologic atypia {1901}. A gestational
sac, amnion, umbilical cord and fetal
tissue are not found {481}. It has re c e n t-
ly been suggested that villous stro m a l
nuclear negative staining for the paternally
imprinted gene product p57 may
be diagnostically useful for confirm i n g
the diagnosis of a complete mole {425}.
The extent of trophoblastic atypia and
hyperplasia do not correlate with the
behaviour in complete mole {776,978}.
In the past most complete hydatidiform
moles were diagnosed early in the second
trimester at an average gestational
age of 14 weeks {1924}. Curre n t l y, with
the widespread use of routine ultrasonography
in pre g n a n c y, complete
moles are diagnosed between 8 and 12
weeks of gestational age {1924}. Moles
diagnosed at this "early" stage diff e r
histologically from moles diagnosed in
the second trimester {1426,1924}.
Although villous cavitation may be minimal
in an "early" mole, other characteristic
villous stromal features are pre s-
ent, including hypercellularity and a
myxoid basophilic stroma (re s e m b l i n g
that of a myxoid fibroadenoma). In addition,
unusual villous shapes with complex
bulbous protrusions ("cauliflowerlike"
villi) and trophoblastic atypia are
p re s e n t .
Somatic genetics
Complete and partial molar pre g n a n-
cies have distinctly diff e rent cytogenetic
origins. Complete moles generally
have a 46,XX karyotype, and the molar
c h romosomes are completely of paternal
origin {1385}. Most complete moles
appear to arise from an anuclear empty
ovum fertilized by a (23X) haploid
s p e rm that then replicates its own chromosomes
{3172}. Whereas most complete
moles have a 46,XX chro m o s o m a l
p a t t e rn, about 10% of complete moles
have a 46,XY karyotype {2197}. The
46,XY complete mole arises from fert i l-
ization of an anuclear empty egg by two
s p e rm. While all chromosomes in a
complete mole are entirely of patern a l
A
Fig. 4.50 Invasive complete hydatidiform mole. A Sectioned surface shows dilated villi and invasion of the myometrium (arrowheads). B Note the molar villus (V)
within a myometrial vein showing a fibroedematous core surrounded by hyperplastic trophoblastic proliferation (P).
B
Gestational trophoblastic disease 253