Invasive breast carcinoma - IARC

Fig. 4.34 Leiomyomas. The sectioned surface shows
typical circumscribed, rubbery, white nodules.
Fig. 4.35 Epithelioid leiomyoma with sex cord-like features. The presence of smooth muscle rules out an
endometrial stromal or pure sex cord-like tumour.
cal appearance. The margins of most
leiomyomas are histogically circ u m-
scribed, but occasional benign tumours
demonstrate interdigitation with the surrounding
myometrium, which may rare l y
be extensive.
Immunoprofile
Smooth muscle neoplasms react with
antibodies to muscle-specific actin,
alpha-smooth muscle actin, desmin and
h-caldesmon. Anomalous expression of
cytokeratin immunoreactivity is observed
frequently both in the myometrium and in
smooth muscle tumours, the extent and
intensity of reactivity depending on the
antibodies used and the fixation of the
specimen. Epithelial membrane antigen
is negative in smooth muscle tumours.
CD10 reactivity may focally be present.
Histological variants
Most subtypes of leiomyoma are chiefly
of interest in that they mimic malignancy
in one or more aspects.
Mitotically active leiomyoma
Mitotically active leiomyomas occur most
often in premenopausal women. They
have the typical macroscopic and histological
appearances of a leiomyoma with
the exception that they usually have 5 or
more mitotic figures per 10 high power
fields {211,2293}. Occasionally, these
smooth muscle tumours contain >15
mitotic figures per 10 high power fields,
in which case the term mitotically active
leiomyoma with limited experience is
used. The clinical evolution is benign,
even if the neoplasm is treated by
myomectomy. It is imperative that this
diagnosis not be used for neoplasms that
exhibit moderate to severe nuclear atypia,
contain abnormal mitotic figures or
demonstrate zones of coagulative
tumour cell necrosis.
Fig. 4.36 Epithelioid leiomyoma. Both tumour cells
on the right and normal myometrium on the left are
immunoreactive for desmin.
Cellular leiomyoma
Cellular leiomyoma accounts for less
than 5% of leiomyomas, and by definition
their cellularity is "significantly" greater
than that of the surrounding myometrium
{211,2101}. The isolated occurrence of
hypercellularity may suggest a diagnosis
of leiomyosarcoma, but cellular leiomyomas
lack tumour cell necrosis and moderate
to severe atypia and have infrequent
mitotic figures. A cellular leiomyoma
comprised of small cells with scanty
cytoplasm can be confused with an
endometrial stromal tumour. This problem
becomes particularly difficult with
what has been termed the highly cellular
leiomyoma.
Haemorrhagic cellular leiomyoma and
hormone induced changes
A haemorrhagic cellular or "apoplectic"
leiomyoma is a form of cellular leiomyoma
that is found mainly in women who
a re taking oral contraceptives or who
either are pregnant or are postpart u m
{1960,2050}. Macroscopic examination
reveals multiple stellate haemorrhagic
a reas. Coagulative tumour cell necro s i s
is generally absent. Normal mitotic figu
res are present and are usually confined
to a narrow zone of granulation
Fig. 4.37 Atypical leiomyoma. This cellular neoplasm
exhibits nuclear pleomorphism but no mitotic
figures or tumour cell necrosis.
240 Tumours of the uterine corpus