Invasive breast carcinoma - IARC

A
B
Fig. 1.88 Large excision biopsy of a high grade ductal
carcinoma in situ. A Note the sharp demarcation
between DCIS, comedo type (left), and adjacent
fibrous stroma. B Mammography showing a large
area with highly polymorphic microcalcifications.
mammogram, the specimen X-ray and
the histologic slides. Since the majority of
DCIS is non palpable, the mammographic
estimate is the sole guide for re s e c t i o n .
T h e re f o re, data on the mammographic
pathological correlation of the tumour size
a re essential for guiding the extent of surg
e ry. The mammographic extent of a
DCIS is defined as the greatest distance
between the most peripherally located
clusters of suspicious micro c a l c i f i c a t i o n s ,
and the histologic extent as the gre a t e s t
distance between the most peripherally
located, histologically verified, DCIS foci.
Histologic evaluation supported by correlation
with the X-ray of the sliced specimen
allows a precise and re p ro d u c i b l e
assessment of the extent of any DCIS
p resent. Whole organ studies have shown
that mammography, on the basis of significant
microcalcifications, generally
u n d e restimates the histologic or "re a l "
size of DCIS by an average of 1-2 cm. In
a series of DCIS cases with mammographic
sizes up to 3 cm, the size diff e r-
ence was less than 2 cm in more than
80% of the cases {1231}.
DCIS may appear as a multifocal pro c e s s
due to the presence of multiple tumour
foci on two-dimensional plane sections.
H o w e v e r, these tumour spots may not
necessarily re p resent separate foci.
Intraductal tumour growth on thre e -
dimensional studies appears to be continuous
rather than discontinuous {831}.
M o re specifically, whereas poorly diff e r-
entiated DCIS shows a pre d o m i n a n t l y
continuous growth, the well diff e re n t i a t e d
DCIS, in contrast, may present a more
discontinuous (multifocal) distribution.
These results have a direct implication on
the reliability of the margin assessment of
surgical specimens. In cases of poorly
d i ff e rentiated DCIS, margin assessment
should, theore t i c a l l y, be more re l i a b l e
than well diff e rentiated DCIS. In a multifocal
process with discontinuous gro w t h ,
the surgical margin may lie between the
tumour foci, giving the false impression of
a free margin.
The distribution of DCIS in the breast is
typically not multicentric, defined as
tumour involvement in two or more re m o t e
a reas separated by uninvolved glandular
tissue of 5 cm. On the contrary, DCIS is
typically ‘segmental’ in distribution
{1230}. In practical terms, this implies that
two apparently separate areas of "malignant"
mammographic micro c a l c i f i c a t i o n s
usually do not re p resent separate fields of
DCIS but rather a larger tumour in which
the two mammographically identified
fields are connected by DCIS, which is
mammographically invisible due to the
lack of detectable size of micro c a l c i f i c a-
tions. One should be aware that single
m i c roscopic calcium particles smaller
than about 80µ cannot be seen on conventional
mammograms.
Grading
Although there is currently no universal
a g reement on classification of DCIS, there
has been a move away from traditional
a rchitectural classification. Most modern
systems use cytonuclear grade alone or
in combination with necrosis and or cell
polarization. Recent international consensus
conferences held on this subject
endorsed this change and re c o m m e n d e d
that, until more data emerges on clinical
outcome related to pathology variables,
grading of DCIS should form the basis of
classification and that grading should be
based primarily on cytonuclear feature s
{6,7,1565,2346}.
Pathologists are encouraged to include
additional information on necrosis, arc h i t e c-
t u re, polarization, margin status, size and
calcification in their re p o rt s .
Depending primarily on the degree of
nuclear atypia, intraluminal necrosis and,
to a lesser extent, on mitotic activity and
Table 1.13
Features of DCIS to be documented for the surgical
pathology report.
Major lesion characteristics
1. Nuclear grade
2. Necrosis
3. Architectural patterns
Associated features
1. Margins
If positive, note focal or diffuse involvement.
Distance from any margin to the nearest
focus of DCIS.
2. Size (either extent or distribution)
3. Microcalcifications (specify within DCIS or
elsewhere)
4. Correlate morphological findings with specimen
imaging and mammographic findings
calcification, DCIS is generally divided
into three grades; the first two features
constitute the major criteria in the majority
of grading systems. It is not uncommon
to find admixture of various grades
of DCIS as well as various cytological
variants of DCIS within the same biopsy
or even within the same ductal space.
When more than one grade of DCIS is
present, the proportion (percentage) of
various grades should be noted in the
diagnosis {2876}. It is important to note
that a three tiered grading system does
not necessarily imply progression from
grade 1 or well differentiated to grade 3
or poorly differentiated DCIS.
Histopathology
Low grade DCIS
Low grade DCIS is composed of small,
monomorphic cells, growing in arcades,
m i c ropapillae, cribriform or solid patterns.
The nuclei are of uniform size and
have a regular chromatin pattern with
inconspicuous nucleoli; mitotic figures
Table 1.14
Minimal criteria for low grade DCIS.
Cytological features
1. Monotonous, uniform rounded cell
population
2. Subtle increase in nuclear-cytoplasmic ratio
3. Equidistant or highly organized nuclear
distribution
4. Round nuclei
5. Hyperchromasia may or may not be present
Architectural features
Arcades, cribriform, solid and/or
micropapillary pattern
Intraductal proliferative lesions
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