Invasive breast carcinoma - IARC

Benign epithelial proliferations
G. Bussolati
F.A. Tavassoli
B.B. Nielsen
I.O. Ellis
G. MacGrogan
L o c a l i z a t i o n
T h e re is little data on location or laterality
of most benign breast lesions. As
with carcinoma, the majority arise within
the terminal duct lobular unit (TDLU). A
major exception is the benign solitary
intraductal papilloma, appro x i m a t e l y
90% of which occurs in the large ducts
in the central region of the bre a s t
{1098}. Other benign lesions specific to
the nipple areolar complex include nipple
adenoma and syringoma and are
discussed in the chapter on nipple.
Clinical features
The predominant presenting symptoms
in women attending a breast clinic are
described in the section on Invasive
C a rcinoma, where signs and symptoms
most likely to be associated with a low
risk of malignancy are described. The
f requency of benign conditions varies
considerably with the age of the patient.
F i b roadenoma is most frequent in
younger patients, other localized benign
lesions and cysts occur most fre q u e n t l y
in women between the ages of 30 and
50. This contrasts with carc i n o m a ,
which is rare below the age of 40.
The mammographic appearances of
benign epithelial lesions are varied but
common lesions such as cysts are typically
seen as well defined or lobulated
mass lesions. Calcification is also a
common feature of fibrocystic change
and sclerosing adenosis. Other benign
lesions such as radial scar, complex
s c l e rosing lesion and fat necrosis can
p roduce ill defined or spiculate mass
lesions, which are indistinguishable
f rom some forms of breast carc i n o m a .
A d e n o s i s
D e f i n i t i o n
A frequent, benign, proliferative pro c e s s
that affects mainly the lobular (acinar)
component of the breast parenchyma.
It can be accompanied by fibro s i s
causing considerable distortion of the
glands simulating an invasive pro c e s s .
F requently it is a small and micro s c o p i c
change, but it may be widespread. In
some instances, it may form a palpable
mass and has been called nodular
adenosis or adenosis tumour. Several
histological types have been described,
but there is not complete agreement on
their designation. Only the most fre q u e n t
variants are discussed.
Radial scar/complex sclerosing lesion
which incorporates a combination of
benign changes including adenosis is
also included in this section.
E p i d e m i o l o g y
This lesion occurs most frequently in
women in their third and fourth decade.
Macroscopy
Adenosis may be non-distinctive, showing
unremarkable fibrous or cystic
b reast tissue. A few cases assume the
appearance of a firm rubbery gre y
mass.
Histopathology
Adenosis in its simplest form is characterized
by a usually loosely structure d
p roliferation of acinar or tubular struct
u res, composed of an epithelial and
myoepithelial cell layer and surro u n d e d
by a basement membrane.
Sclerosing adenosis
S c l e rosing adenosis (SA) is characterized
by a compact proliferation of acini
with preservation of the luminal epithelial
and the peripheral myoepithelial
(ME) cell layers along with a surro u n d-
ing basement membrane. These elements
can easily be demonstrated by
immunohistochemical staining for keratin,
smooth-muscle actin and laminin,
re s p e c t i v e l y. Although compression or
attenuation of the acini by surro u n d i n g
f i b rosis may be marked, sclero s i n g
adenosis nearly always retains an
organic or lobulated configuration often
best observed at low power view.
M i c rocalcifications are common within
Fig. 1.107 Sclerosing adenosis. Typical organic
configuration of the lesion.
Fig. 1.108 Sclerosing adenosis. The myoepithelial
cells are prominent with immunostain for smooth
muscle actin.
the glands. Areas of apocrine metaplasia
are also common. Rarely neural
invasion is encountered and vascular
invasion has been re p o rted {149}.
Lesions which form a mass show
adenosis with a mixture of growth patt
e rns {2015}, the most frequent of which
is sclerosing adenosis.
In rare cases sclerosing adenosis may
be involved by DCIS or LIN {1046,
1275a,1846a,2015,2336a,3104a}.
Differential diagnosis
S c l e rosing adenosis can mimic invasive
c a rcinoma. The overall lobulated arc h i-
t e c t u re, persistence of ME cells, and
lack of epithelial atypia help to exclude
carcinoma {321,1046}. In cases involved
by in situ carcinoma, the immunohistochemical
demonstration of persistent
myoepithelial cells is crucial in excluding
invasion.
Benign epithelial proliferations
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