Invasive breast carcinoma - IARC

Treatment of ILC should depend on the
stage of the tumour and parallel that of
IDC. Conservative treatment has been
shown to be appropriate for ILC {327,
2205,2269,2541,2570,2696}.
Tubular carcinoma
Definition
A special type of breast carcinoma with a
particularly favourable prognosis composed
of distinct well differentiated tubular
structures with open lumina lined by a
single layer of epithelial cells.
ICD-O code 8211/3
Epidemiology
P u re tubular carcinoma accounts for
under 2% of invasive breast cancer in
most series. Higher frequencies of up
to 7% are found in series of small T1
b reast cancers. Tubular cancers are
often readily detectable mammographically
because of their spiculate nature
and associated cellular stroma and are
seen at higher frequencies of 9-19%, in
mammographic screening series {1853,
2192,2322}.
When compared with invasive carcinomas
of no special type (ductal NOS),
tubular carcinoma is more likely to occur
in older patients, be smaller in size and
have substantially less nodal involvement
{691,1379,2166}.
These tumours are recognized to occur
in association with some epithelial proliferative
lesions including well differentiated/low
grade types of ductal carcinoma
in situ (DCIS), lobular neoplasia and flat
epithelial atypia {915,1034}. In addition,
an association with radial scar has been
proposed {1668,2725}.
Macroscopy
There is no specific macroscopical feature
which distinguishes tubular carcinoma
from the more common ductal no
special type (NOS) or mixed types, other
than small tumour size. Tubular carcinomas
usually measure between 0.2 cm
and 2 cm in diameter; the majority are 1
cm or less {772,1829,2081}.
Two morphological subtypes have been
described, the 'pure' type which has a
pronounced stellate configuration with
radiating arms and central yellow flecks
due to stromal elastosis and the sclerosing
type characterized by a more diffuse,
ill defined structure {410,2190}.
Histopathology
The characteristic feature of tubular carc i-
noma is the presence of open tubules
composed of a single layer of epithelial
cells enclosing a clear lumen. These
tubules are generally oval or rounded and,
t y p i c a l l y, a pro p o rtion appears angulated.
The epithelial cells are small and
regular with little nuclear pleomorphism
and only scanty mitotic figures. Multilayering
of nuclei and marked nuclear
pleomorphism are contraindications for
diagnosis of pure tubular carc i n o m a ,
even when there is a dominant tubular
architecture. Apical snouts are seen in as
many as a third of the cases {2874}, but
a re not pathognomonic. Myoepithelial
cells are absent but some tubules may
have an incomplete surrounding layer of
basement membrane components.
Fig. 1.23 Tubular carcinoma. Specimen X-ray.
A secondary, but important feature is
the cellular desmoplastic stroma, which
accompanies the tubular structure s .
Calcification may be present in the invasive
tubular, associated in situ or the
s t romal components.
DCIS is found in association with tubular
carcinoma in the majority of cases; this
is usually of low grade type with a
c r i b r i f o rm or micro p a p i l l a ry pattern .
Occasionally, the in situ component is
lobular in type. More recently an association
has been described with flat epithelial
atypia and associated micropapillary
DCIS {915,1034}.
T h e re is a lack of consensus concern i n g
the pro p o rtion of tubular structure s
re q u i red to establish the diagnosis
of tubular carcinoma. In the pre v i o u s
WHO Classification {1,3154} and a
number of published studies {410,1350,
1832} no specific cut-off point is indicated
although there is an assumption that all
the tumour is of a tubular configuration.
Some authors have applied a strict 100%
rule for tubular structures {409,552, 2190},
some set the pro p o rtion of tubular struct
u res at 75% {1668,1829, 2224,2442}, and
A
Fig. 1.24 Tubular carcinoma. A There is a haphazard distribution of rounded and angulated tubules with open lumens, lined by only a single layer of epithelial cells
separated by abundant reactive, fibroblastic stroma. B The neoplastic cells lining the tear-drop shaped tubules lack significant atypia.
B
26 Tumours of the breast