Invasive breast carcinoma - IARC

Table 1.15
Differential diagnosis of benign papilloma and intraductal papillary carcinoma.
Feature Papilloma Papillary intraductal carcinoma
Cell types covering fibrovascular stalks Epithelial and myoepithelial Epithelial (myoepithelial cells may be seen at
periphery of duct wall)*
Nuclei Normochromatic vesicular chromatin; May be hyperchromatic, with diffuse
variable in size and shape
chromatin: relatively uniform in size and shape
Apocrine metaplasia Frequent Absent
Fibrovascular stalks Usually broad and present throughout lesion; Often fine and may be absent in some areas;
may show sclerosis
sclerosis uncommon
Immunohistochemical markers for myoepithelial Positive Negative*
cells (e.g. smooth muscle actin, HMW-CK
[such as CK 5/6])
* Myoepithelial cells may be present in some papillary carcinomas–see text for explanation.
with concomitant usual ductal hyperplasia,
atypical intraductal hyperplasia,
ductal carcinoma in situ or invasive carcinoma
as well as with sclerosing adenosis
or radial scar {1097,1945,2091,2092}.
The term micropapilloma has been
applied to the smallest type of peripheral
papillomas corresponding to multiple
microscopic papillomas that grow in foci
of adenosis. Collagenous spherulosis,
consisting of round eosinophilic
spherules of basement membrane (type
IV collagen), edged by myoepithelial
cells may be seen in some peripheral
papillomas.
Atypical papilloma
Atypical intraductal papillomas are characterized
by the presence of a focal
atypical epithelial proliferation with low
grade nuclei. Such intraepithelial proliferations
may occasionally resemble atypical
ductal hyperplasia (ADH) or small
foci of low grade DCIS.
Prognosis and predictive features
of benign and atypical papillomas
The risk of subsequent invasive carcinoma
associated with papillomas or atypical
papillomas should be appreciated in
the context of the surrounding breast tissue.
A benign papilloma without surrounding
changes is associated with a
slightly increased relative risk of subsequent
invasive breast carcinoma, similar
to that of moderate or florid usual ductal
hyperplasia in the breast pro p e r
{885,2151}. The relative risk associated
with peripheral papilloma may be higher
compared to central papilloma. However,
this risk also depends on the concurrent
presence of other forms of proliferative
disease and as yet no study has been
designed to specifically answer this
question {2151}. There is disagreement
as to whether the risk of subsequent
invasive breast carcinoma applies only to
the same site in the ipsilateral breast or
applies to both breasts {2151,2326}. The
significance of atypia within a papilloma
is still not clear and is obscured by the
frequent concurrent presence of atypia
within the surrounding breast parenchyma.
It appears that if epithelial atypia is
confined to the papilloma without surrounding
proliferation or atypia the risk of
subsequent invasive breast carcinoma is
similar to that of non-atypical papilloma.
As expected, epithelial atypia when
present simultaneously both within and
outside a papilloma is associated with a
moderate to highly increased relative risk
{2151}; this is not a reflection of the risk
associated with pure atypical papilloma,
however.
The standard treatment for papillomas
has been complete excision with microscopic
assessment of surro u n d i n g
breast tissue. Because of potential variability
within a papillary lesion, complete
excision is prudent, regardless of the
findings in a previous core biopsy.
The differential diagnosis of benign and
malignant papillary lesions on fro z e n
section can be extremely difficult and a
definitive diagnosis should always be
made only after examination of paraffin
embedded material.
Intraductal papillary carcinoma
ICD-O code 8503/2
Synonym
P a p i l l a ry carcinoma, non-invasive.
Definition
This lesion is located within a variably
distended duct and may extend into its
branches. It is characterized by pro l i f-
eration of fibrovascular stalks and its
diagnosis re q u i res that 90% or more of
A
B
Fig. 1.102 Central papilloma. A An arborescent
structure composed of papillary fronds within a
dilated duct. B Myoepithelial hyperplasia with SMA
positive “myoid” transformation.
78 Tumours of the breast