Invasive breast carcinoma - IARC

A
B
C
Fig. 4.43 Carcinosarcoma. A A biphasic tumour is composed of poorly differentiated malignant glands and sarcomatous elements. B A biphasic tumour is composed
of a solid aggregate of malignant epithelium with central squamous differentiation and sarcomatous elements. Mitoses are frequent. C High power image shows a
mesenchymal component resembling rhabdomyosarcoma. D High power image shows a mesenchymal component resembling osteosarcoma.
D
form of rhabdomyoblasts, although other
elements such as osteosarcoma and
liposarcoma may rarely occur.
In general, both carcinomatous and sarcomatous
elements are easily identifiable,
although in some cases one or
other element may form a minor component
that may be only identified following
extensive sampling of the neoplasm. Any
uterine neoplasm composed of high
grade sarcoma, especially when heterologous
elements are present, should be
extensively sampled in order to rule out a
c a rc i n o s a rcoma or sarcomatous overgrowth
in an adenosarcoma. In most
instances the two elements are sharply
demarcated, but in some they appear to
merge with transitional forms between
the two elements. Eosinophilic hyaline
inclusions are commonly seen, especially
in the sarcomatous elements {2359}.
Occasionally, a carcinosarcoma may be
identified in an otherwise benign
endometrial polyp. A uterine carcinosarcoma
with a component of yolk sac
tumour has been described in a patient
with an elevated serum alpha-fetoprotein
level {2665}. Occasional tumours with a
rhabdoid phenotype {190} or a malignant
neuroectodermal component {931} have
also been described. Occasional uterine
carcinosarcomas of mesonephric origin
have been reported {3171}. Other unusual
histological features include
melanocytic {77} and neuro e n d o c r i n e
differentiation {537}.
Immunoprofile
In general, the epithelial elements are
i m m u n o reactive with anti-cytokeratin
antibodies and the mesenchymal elements
with vimentin. The mesenchymal
elements often show focal staining with
anti-cytokeratin antibodies supporting an
epithelial origin of this component. The
usual concordance of TP53 stains
between the epithelial and mesenchymal
components supports a common monoclonal
origin for both elements {1796,
2827}. Desmin, myoD1, myoglobin and
sarcomeric actin staining may highlight a
r h a b d o m y o s a rcomatous mesenchymal
component. Cartilaginous elements usually
stain with S-100 protein.
Histogenesis
It should be noted that clinical, immunohistochemical,
ultrastructural and molecular
studies have all suggested that carcinosarcomas
are really metaplastic carcinomas
in which the mesenchymal component
retains at least some epithelial
features in the vast majority of cases
{1809}. Though still classified as "mixed"
by convention, these tumours are perhaps
better considered subsets of
endometrial carcinoma and cert a i n l y
should not be grouped histogenetically
or clinically with uterine sarc o m a s
{1810}. On the other hand, the tumours
other than carcinosarcoma in this group
are considered to be true mixed tumours.
246 Tumours of the uterine corpus