Invasive breast carcinoma - IARC

aged women (average age of presentation
is 40-50 years) around 15-20 years
older than for FAs.
In Asian countries, PTs occur at a younger
age (average 25-30 years) {487}.
Malignant PTs develop on average 2-5
years later than benign PTs. Among
Latino whites, especially those born in
Central and South America, malignant
phyllodes is more frequent {254}.
Isolated examples of PTs in men have
been recorded {1424a,2023}.
Aetiology
P Ts are thought to be derived fro m
intralobular or periductal stroma. They
may develop de novo or from FAs. It is
possible, in rare cases, to demonstrate
the presence of a pre-existing FA adjacent
to a PT.
Clinical features
Usually, patients present with a unilateral,
firm, painless breast mass, not attached
to the skin. Very large tumours (>10 cm)
may stretch the skin with striking distension
of superficial veins, but ulceration is
very rare. Due to mammographic screening,
2-3 cm tumours are becoming more
common, but the average size remains
around 4-5 cm {775,2425}. Bloody nipple
discharge caused by spontaneous
i n f a rction of the tumour has been
described in adolescent girls {1781,
2833}. Multifocal or bilateral lesions are
rare {1932}.
Imaging reveals a rounded, usually
sharply defined, mass containing clefts
or cysts and sometimes coarse calcifications.
Macroscopy
P Ts form a well circumscribed firm ,
bulging mass. Because of their often
clearly defined margins, they are often
shelled out surgically.
The cut surface is tan or pink to grey and
may be mucoid. The characteristic
whorled pattern with curved clefts
resembling leaf buds is best seen in
large lesions, but smaller lesions may
have an homogeneous appearance.
Haemorrhage or necrosis may be present
in large lesions.
Histopathology
PTs typically exhibit an enhanced intracanalicular
growth pattern with leaf-like
p rojections into dilated lumens. The
epithelial component consists of luminal
A
B
Fig. 1.152 Phyllodes tumour, borderline. A A predominantly pushing margin in a borderline tumour.
B Periductal stromal condensation. C Dense spindle-cell stroma with a few mitotic figures.
C
epithelial and myoepithelial cells.
Apocrine or squamous metaplasia is
occasionally present and hyperplasia is
not unusual. In benign phyllodes
tumours, the stroma is more cellular than
in FAs, the spindle cell nuclei are
monomorphic and mitoses are rare. The
stromal cellularity may be higher in zones
in close contact with the epithelial component.
Areas of sparse stromal cellularity,
hyalinisation or myxoid changes are
not uncommon. Necrotic areas may be
seen in very large tumours. The presence
of occasional bizarre giant cells
should not be taken as a mark of malignancy.
Lipomatous, cartilagenous and
osseous metaplasia have been reported
{2057,2730}. The margins are usually
well delimited, although very small
tumour buds may protrude into the surrounding
tissue. Such expansions may
be left behind after surgical removal and
are a source of local recurrence.
Malignant PTs have infiltrative rather than
pushing margins. The stroma shows
frankly sarcomatous, usually fibrosarcomatous
changes. Heterologous differentiation
such as liposarcoma, osteosarcoma,
chondrosarcoma or rhabdomyosarcoma
may occur {536,1161,2057,2249,
2308}. Such changes should be indicated
in the diagnostic report. Due to overgrowth
of the sarcomatous components,
the epithelial component may only be
identified after examining multiple sections.
Borderline PTs (or low grade malignant
PTs) display intermediate features and
the stroma often resembles low-grade
fibrosarcoma.
Malignant epithelial transformation (DCIS
or LIN and their invasive counterparts) is
uncommon {2136}.
Differential diagnosis
Benign PTs may be difficult to distinguish
from fibroadenomas. The main
f e a t u res are the more cellular stro m a
and the formation of leaf-like pro c e s s e s .
H o w e v e r, the degree of hyperc e l l u l a r i t y
that is re q u i red to qualify a PT at its
lower limit is difficult to define. Leaf-like
Fibroepithelial tumours 101