Invasive breast carcinoma - IARC

Fig. 1.148 Phyllodes tumour. A well circumscribed 6.5
cm mass with a few clefts was histologically benign.
Fig. 1.149 Phyllodes tumour. A circumscribed 9 cm
tumour contained a large yellow nodule of liposarcoma
(yellow) adjacent to a nodule of malignant
phyllodes tumour (pink).
Differential diagnosis
Most FAs, especially those of large size,
cellular stroma and epithelial clefts need
to be distinguished from phyllodes
tumours (see below). Another bre a s t
lesion, which can simulate FA, is hamartoma.
Prognosis and predictive features
Most FAs do not recur after complete
surgical excision. In adolescents, there
is a tendency for one or more new
lesions to develop at another site or even
close to the site of the previous surgical
t re a t m e n t .
The risk of developing cancer within a
FA or in breasts of patients pre v i o u s l y
t reated for FA is low, although a slightly
i n c reased risk has been re p o rted {734,
1 6 4 0 } .
Phyllodes tumours
Definition
A group of circumscribed biphasic
tumours, basically analogous to fibroadenomas,
characterized by a double
l a y e red epithelial component arranged
in clefts surrounded by an overgro w i n g
h y p e rcellular mesenchymal component
typically organized in leaf-like struct
u res.
Phyllodes tumours (PTs) are usually
benign, but recurrences are not uncommon
and a relatively small number of
patients will develop haematogenous
metastases. Depending on the bland or
o v e rtly sarcomatous characteristics of
their mesenchymal component (also
called stromal component), PTs display a
morphological spectrum lying between
fibroadenomas (FAs) and pure stromal
sarcomas.
Still widespread in the literature, the
generic term “cystosarcoma phyllodes”,
is currently considered inappro p r i a t e
and potentially dangerous since the
majority of these tumours follow a benign
course. It is highly preferable to use the
neutral term “phyllodes tumour”, according
to the view already expressed in the
WHO classification of 1981 {3154}, with
the adjunction of an adjective determining
the putative behaviour based on histological
characteristics.
ICD-O codes
Phyllodes tumour, NOS 9020/1
Phyllodes tumour, benign 9020/0
Phyllodes tumour, borderline 9020/1
Phyllodes tumour, malignant 9020/3
Periductal stromal sarcoma,
low grade 9020/3
A
Fig. 1.150 Benign phyllodes tumour. A Leaf-like pattern and well defined interface with the surrounding
normal tissue. B Higher magnification shows stromal cellularity.
B
Epidemiology
In western countries, PTs account for 0,3-
1% of all primary tumours and for 2,5% of
all fibroepithelial tumours of the breast.
They occur predominantly in middle-
A
Fig. 1.151 Malignant phyllodes tumour. A Periductal stromal growth with malignant features. B Note severe stromal atypia and multiple mitoses.
B
100 Tumours of the breast