Invasive breast carcinoma - IARC

cause obvious diagnostic pro b l e m s .
Sometimes a papillary pattern may be
a p p a rent. Ultrastructural examination
shows the long slender microvilli characteristic
of mesothelial cells.
Immunoprofile
Immunohistochemical positivity with anticytokeratin
antibodies and anti-mesothelial
antibodies, such as HBME1 and calretinin,
is usual. This finding may be useful
in the distinction between adenomatoid
tumour and lymphangioma. There is
no reactivity with Ber-EP4, helping to
exclude a carcinoma in those cases that
have signet-ring cell morphology {211,
2101,2123}.
Histogenesis
The histogenesis has been debated in
the past, but immunohistochemical and
ultrastructural studies have shown these
neoplasms to be of mesothelial origin.
When located within the uterus {654,
2041,2311,2768,2924}, they are probably
derived from the serosal mesothelium.
Prognosis and predictive factors
Adenomatoid tumours are invariably
benign with no risk of recurrence or
metastasis.
Rare mesenchymal tumours
Definition
A variety of mesenchymal tumours, both
malignant and benign, occurring within
the uterus that are not endometrial stromal,
smooth muscle or mesothelial in
type. These are rare and are identical
histologically to their counterparts arising
in more usual sites.
Malignant tumours
In cases of malignancy the neoplasm
should be extensively sampled in order
to exclude sarcomatous overgrowth in a
MMMT or an adenosarcoma. The most
common of these neoplasms to arise in
the uterus is rhabdomyosarcoma {716,
1149,1814,2112}. The latter is usually of
embryonal type in young females and of
pleomorphic type in the middle aged or
elderly. Occasional cases of uterine alveolar
rhabdomyosarcoma have also been
described {475}. Occasional re s i d u a l
entrapped benign endometrial glands
may be present, especially towards the
surface of these neoplasms. That finding
should not be taken as evidence of an
a d e n o s a rcoma. Other malignant mesenchymal
neoplasms described in the
uterus include malignant fibrous histiocytoma
{1404}, angiosarcoma (including
the epithelioid variant) {2551,2853},
liposarcoma {180}, osteosarcoma {784,
1137,1844}, c h o n d ro s a rc o m a { 1489 },
alveolar soft part sarcoma {2319}, Ewing
t u m o u r, malignant peripheral nerve
sheath tumour, malignant pigmented
n e u ro e c t o d e rmal tumour of infancy
{2580} and peripheral primitive neuroect
o d e rmal tumour {638,1894,2017}. In
general, these are all bulky neoplasms,
frequently high stage at presentation,
and the histology is similar to their counterparts
elsewhere. Immunohistochemical
studies may assist in establishing a
definitive diagnosis.
H a e m a n g i o p e r i c y t o m a has also been
described in the uterus, but it is likely that
most of the reported cases represent
vascular endometrial stromal neoplasms
{2693}.
Malignant rhabdoid tumours have also
been described {948,1255}. Since a rhabdoid
component may rarely be found in an
otherwise typical endometrial stromal neoplasm
{1813}, it is possible that some
rhabdoid tumours re p resent an unusual
histological variant of an endometrial stromal
or some other neoplasm. As with other
e x t r a renal rhabdoid tumours, the uterine
neoplasm may re p resent a peculiar histological
growth pattern that may be found in
a variety of neoplasms; there f o re, extensive
sampling should be undertaken to
exclude a diagnosis of rhabdoid diff e re n t i-
ation in another more common neoplasm.
Only when other elements are not identified
should a diagnosis of uterine malignant
rhabdoid tumour be considere d .
Benign tumours
Benign tumours include lipoma, haemangioma,
lymphangioma and rhabdomyoma
{466,686}. Occasional uterine myxomas
have been described in Carney
s y n d rome {2654}. Before diagnosing
these entities, a lipoleiomyoma should be
excluded in the case of lipoma, a vascular
leiomyoma in the case of haemangioma,
an adenomatoid tumour in the
case of lymphangioma and a myxoid
smooth muscle neoplasm in the case of
myxoma. A single case of postoperative
spindle cell nodule of the endometrium
that occurred following a uterine curettage
has been described {504}.
244 Tumours of the uterine corpus