Invasive breast carcinoma - IARC

Fig. 1.160 CD20 immunoexpression in diffuse large
B-cell lymphoma.
The relationship of the surrounding mammary
tissue to the lymphomatous infiltration
differs from case to case. In some,
the bulk of the lesion is located in the
subcutaneous tissue, and bre a s t
parenchyma is found only peripherally.
In others, numerous ducts and lobules
are embedded in the infiltrate but clearly
separated from it. Sometimes lymphoma
cells infiltrate the ducts to diff e re n t
degrees and, in rare cases, the latter are
overgrown by lymphoma cells and barely
visible, sometimes revealed only by
using keratin immunostaining. The stroma
may be scant or abundant and the
infiltrates may have a “medullary ”
appearance. In some cases, lymphoma
cells form cords and ribbons simulating
an infiltrating lobular carc i n o m a .
Diffuse large B-cell lymphoma
ICD-O code 9680/3
Lymphoma of this type is characterized
by a diffuse pattern of infiltration of bre a s t
tissue by large lymphoma cells varying in
appearance from quite uniform to pleomorphic.
Generally, the lymphoma cells
resemble centroblasts or immunoblasts.
The nuclei are oval, indented or even
lobated, usually with distinct, single or
multiple nucleoli, and the amount of cytoplasm
is variable. Mitoses are usually
n u m e rous, various numbers of cells are
apoptotic and necrotic foci may be found.
Lymphoma cells are often admixed with
smaller reactive lymphocytes of B or T
type; macrophages may be pro m i n e n t ,
i m p a rting a “starry sky” appearance to
the tumour. In some cases, pseudofollicular
structures are seen due to selective
infiltration of ductal-lobular units {18}.
Adjacent mammary tissue may exhibit
lobular atrophy or lymphocytic lobulitis
{18,113}; the latter may be prominent and
w i d e s p read, featuring lymphocytic mastopathy
{113}.
Lymphoma cells are immunoreactive for
CD20, CD79a, and CD45RB and negative
for CD3 and CD45RO. Cases with
immunoblastic features may demonstrate
light chain restriction. Exceptionally, lymphoma
cells express CD30 antigen {18}.
Burkitt lymphoma
ICD-O code 9687/3
The morphological features of Burkitt
lymphoma of the breast are identical
with those seen in such a lymphoma in
other organs and tissues: the infiltrate is
composed of sheets of uniform, primitive
looking, cells of medium size, with
round nuclei, multiple nucleoli, coarse
c h romatin and a rather thick nuclear
membrane. The cells are cohesive and
the cytoplasm is moderate in amount
with fine vacuoles containing lipids; it
s q u a res off with the cytoplasm of adjacent
cells. Mitoses are very numero u s .
N u m e rous tingible-body macro p h a g e s
a re evenly dispersed among the neoplastic
cells producing the characteristic,
but by no means pathognomonic,
“ s t a r ry sky” appearance of the lymphoma.
The breast tissue is usually
hyperplastic and secre t o ry.
Patients are usually pregnant or lactating
women, particularly from tro p i c a l
Africa where Burkitt lymphoma is
endemic {2643}. Less fre q u e n t l y, nonendemic,
sporadic cases, primarily presenting
in the breasts, have been
observed {1378}. Tumours typically
p resent with massive bilateral bre a s t
swelling {2643}.
Fig. 1.161 Burkitt lymphoma. Bilateral breast
involvement may be the presenting manifestation
during pregnancy and puberty. BL cells have prolactin
receptors.
I m m u n o h i s t o c h e m i c a l l y, pan-B markers
a re positive, surface Ig, usually of IgM
type, is also positive. In addition, CD10
and bcl-6 are commonly positive, while
CD5, bcl-2 and TdT are negative. EBV
is frequently demonstrated in endemic
but not in sporadic cases. IgH and IgL
genes are re a r r a n g e d .
Extranodal marginal-zone B-cell
lymphoma of MALT type
ICD-O code 9699/3
At least some breast lymphomas
appear to belong to the category of
M A LT lymphomas although the data
on their frequency vary substantially.
The breast was suggested to be one
component of a common mucosal immune
system {268} and may acquire
lymphoid tissue as a part of an autoimmune
process {2585} within which
the lymphoma may develop. A number
of recent series on breast lymphoma
include examples of MALT lymphoma
{534,994,1261,1580,1792}; they were
not encountered in other series {117,
296,1346,1665}.
C l a s s i c a l l y, MALT lymphomas are composed
of small lymphocytes, marginal
zone (centrocyte-like) and/or monocytoid
B-cells, often interspersed with
larger blastic cells. Monotypic plasma
cells may be numerous and sometimes
p redominant. The infiltrate is diff u s e
and neoplastic colonization of pre - e x i s-
tent reactive follicles may be seen. A
lymphoepithelial lesion, defined originally
as an infiltration of glandular
epithelium by clusters of neoplastic
c e n t rocyte-like cells {1305}, is rare l y
seen. Neoplastic infiltration and destruction
of mammary ducts by lymphoma
cells, most commonly encount
e red in large B-cell lymphomas or infiltration
of ductal epithelium by non-neoplastic
T cells should not be confused
with a true lymphoepithelial lesion.
H o w e v e r, the presence of such a lesion
is not a pre requisite for a diagnosis of
M A LT lymphoma.
I n f l a m m a t o ry reactive conditions may
mimic MALT lymphomas; perhaps
many cases previously described as
pseudolymphoma were in reality MALT
lymphomas given enough time to follow
their evolution.
I m m u n o h i s t o c h e m i c a l l y, MALT lymphoma
expresses pan-B cell markers
108 Tumours of the breast