Invasive breast carcinoma - IARC

Table 1.07
Criteria for the differential diagnosis of mucin producing carcinomas.
Histological type Location of mucin Growth pattern In situ component
Mucinous (colloid) Extracellular Clusters of cells Ductal
carcinoma
in mucus lakes
Mucinous Intracellular and Large cysts, columnar Ductal
cystadenocarcinoma extracellular cells, epithelial
stratification, papillae,
solid areas
Columnar mucinous Intracellular Round and convoluted Ductal
carcinoma
glands lined by a single
layer of columnar cells
Signet ring cell carcinoma Intracellular Isolated cells, cords, Mainly
clusters
lobular
cystic variant numerous cysts of variable
size are formed, some with papill
a ry fronds lined by a single layer of predominantly
bland appearing, columnar
mucinous cells. Focal atypia characterized
by nuclear pleomorphism (but
sparse mitotic activity), loss of polarity
and eosinophilic cellular transform a t i o n
is invariably present, as is invasion of
s u r rounding stroma by most often the
eosinophilic cells. Axillary node metastases
occur in a quarter of mucinous
c y s t a d e n o c a rc i n o m a s .
The columnar cell variant is composed
of a compact to loose aggregation of
round and convoluted glands lined by a
single layer of generaly tall, columnar
mucimous epithelium with bland, basal
nuclei and rare mitotic figure s .
Prognosis and predictive factors
After a maximum follow-up of only 2
years, none of the patients has developed
a re c u r rence or metastasis.
Signet ring cell carcinoma
ICD-O code 8490/3
Signet ring cell carcinomas are of two
types. One type is related to lobular carcinoma
and is characterized by large
intracytoplasmic lumina which comp
ress the nuclei towards one pole of the
cell {1849}. Their invasive component
has the targetoid pattern of classical
lobular carcinoma. The other type is
similar to diffuse gastric carcinoma, and
is characterized by acidic mucosubstances
that diffusely fill the cytoplasm
and dislodge the nucleus to one pole of
the cell. This type of signet ring cell carcinoma
can be seen in association with
the signet ring cell variant of DCIS
{ 1 1 4 3 } .
Neuroendocrine tumours
Definition
P r i m a ry neuroendocrine (NE) carc i n o-
mas of the breast are a group, which
exhibits morphological features similar
to those of NE tumours of both gastro i n-
testinal tract and lung. They expre s s
n e u roendocrine markers in more than
50% of the cell population. Breast carc i-
noma, not otherwise specified, with focal
endocrine diff e rentiation, revealed by
immunocytochemical expression of neuroendocrine
markers in scattered cells,
is not included this gro u p .
Synonym
Endocrine carcinoma.
Epidemiology
NE breast carcinomas re p resent about
2-5% of breast carcinomas. Most patients
a re in the 6th or 7th decades of life {2535}.
N e u roendocrine diff e rentiation also
occurs in male breast carcinoma {2591}.
Clinical features
There are no notable or specific differences
in presentation from other tumour
types. Patients often present with a palpable
nodule, which usually appears as
a circumscribed mass on mammographic
and ultrasound examination.
Patients with small cell carcinoma
often present at an advanced stage.
Endocrine hormone related syndro m e s
a re exceptionally rare. Of interest is the
i n c rease in the blood of neuro e n d o c r i n e
markers such as chromogranin A.
Macroscopy
NE breast carcinomas can grow as infiltrating
or expansile tumours. The consistency
of tumours with mucin production
is soft and gelatinous.
Histopathology
Most NE breast carcinomas form alveolar
structures or solid sheets of cells with a
tendency to produce peripheral palisading.
However, they may present as different
subtypes, depending on the cell
type, grade, degree of differentiation and
presence of mucin production. The latter
is observed in 26% of cases {2535}.
Solid neuroendocrine carcinoma
These tumours consist of densely cellul
a r, solid nests and trabeculae of cells
that vary from spindle to plasmacytoid
and large clear cells {2536} separated
by delicate fibrovascular stroma. In
some tumours, the nests are packed
into a solitary, well defined to lobulated
mass; the tumour cells rarely form
rosette-like structures and display
peripheral palisading reminiscent of
c a rc i n o i d t u m o u r.
Some of these appear to originate fro m
s o l i t a ry, solid papillary intraductal carc i-
nomas. Others form multiple, often ro u n d-
ed solid nests separated by a dense, collagenous
stroma resembling the alveolar
p a t t e rn of invasive lobular carc i n o m a .
Mitotic activity ranges from 4 in the carc i-
noid-like tumour to 12 in the alveolar variant;
focal necrosis may be seen. The
tumour cells contain NE granules.
Small cell / oat cell carcinoma
ICD-O codes
Small cell carcinoma 8041/3
Oat cell carcinoma 8042/3
This is morphologically indistinguishable
from its counterpart in the lung
on the basis of histological and
immunohistochemical features {2662}.
The tumours are composed of densely
packed hyperc h romatic cells with scant
cytoplasm and display an infiltrative
g rowth pattern. An in situ component
with the same cytological features may
32 Tumours of the breast