Ductal Carcinoma
In Situ
377
the “nuclear grade
+
proliferation index” (N
+
P) system.
The N
+
P methodology utilizes automated assessment of
the proliferation index that has been shown to be a repro-
ducible grading system for DCIS as well as for invasive car-
cinoma.
224
Cases of DCIS that have a high proliferation rate
by IHC, and are positive for HER2, confer a higher risk of
recurrence, independent of grade and age.
225
The
bcl-2
gene plays a role in control of cell growth by
inhibiting apoptosis (Fig. 11.32). The expression of bcl-2 in
DCIS is inversely related to grade. Loss of bcl-2 expression is
most pronounced in high-grade DCIS and is directly related
to p53 expression.
128
High-grade DCIS exhibit a higher rate
of apoptosis (apoptotic index) than low-grade lesions.
226
Cytogenetics and Molecular Genetics
Prior to the development of microdissection techniques, few
genetic studies of DCIS were reported because of the technical
difficulties inherent in isolating the epitheliumof these micro-
scopic lesions. DNA extracted from ducts containing DCIS
isolated by microdissection has provided the material for the
molecular analysis of genetic alterations. Using this method,
Radford et al.
227
reported loss of heterozygosity (LOH) on 17p
in 29% of DCIS, compared with normal, control DNA. No
significant difference in the frequency of LOH was observed
among subtypes of DCIS (comedo vs. noncomedo) or in re-
gard to nuclear grade. Another study revealed LOH on chro-
mosome 17p13.1 in 5 of 15 informative cases studied.
228
LOH
on 11p15 has been reported in a high proportion of microdis-
sected samples of DCIS.
229
Chuaqui et al.
230
reported finding
LOH on 11q13 in 6 (27.3%) of 22 DCIS. All of the lesions with
LOH were high grade. LOH was also found in 1 of 11 lesions
(9%) classified as atypical duct hyperplasia. The accumulated
data suggest that LOH occurs often and early in the develop-
ment of DCIS and that the sites of LOH are probable loci of
one or more tumor suppressor genes.
231,232
Stratton et al.
233
detected LOH on 16q in 28% and on 17p
in 29% of DCIS not associated with invasive lesions. DCIS
found in conjunction with invasive carcinomas had a greater
frequency of LOH on chromosomes 16q (55%) and 17p
(52%). Analysis of intraductal and invasive carcinoma from
the same patient has usually but not always shown similar
patterns of LOH in both components.
234–237
This is of par-
ticular interest because there is also a strong correlation be-
tween the distribution of prognostic markers in intraductal
and invasive duct carcinoma, usually with identical patterns
of expression for hormone receptors, HER2, p53, EGFR,
and cyclin D1. Studies by Barsky et al.
238
suggest that DCIS
often has many of the biologic characteristics of invasive
carcinoma, and they hypothesize that the most significant
difference between
in situ
and invasive carcinoma lies in the
inhibitory influences of myoepithelial cells. As previously
noted, studies performed by these investigators indicated
that one or more proteins secreted by myoepithelial cells in-
hibit invasion and angiogenesis.
A study of alterations in chromosome 1 revealed that the
cells in individual ducts from a single specimen of DCIS may
have different genetic patterns.
235
Similar observations were
reported by Marsh and Varley,
239
who analyzed LOH at 9p
in multiple microdissected ducts from individual patients.
LOH was found in 12 of 13 cases studied. Loss of at least one
marker was detected in all subtypes (comedo, solid, cribri-
form, and micropapillary), but the most extensive loss was
present in comedo and cribriform lesions. The pattern of
LOH in DCIS was present in the corresponding invasive car-
cinoma in some but not all tumors. Aubele et al.
240
applied
CGH to microdissected examples of extensive DCIS with
small foci of invasive carcinoma. The procedure detected
“multiple genetic changes affecting 6 to 19 different chromo-
somal regions per tumor (mean 13.6 ± 5.4)” in DCIS. “Chro-
mosomal alterations identified in more than one-third of the
invasive lesions were mainly identical” to those in the cor-
responding DCIS, except for gains of DNA on 3p and 12q,
which were found more frequently in invasive carcinomas.
A remarkable molecular genetic study of DCIS reported
by Waldman et al.
241
employed CGH to detect chromosomal
alterations in primary lesions and in subsequent local breast
recurrences. Paired samples from 18 patients were studied,
with all recurrences being entirely intraductal and detected
16 months to 9.3 years after initial treatment. In 17 cases,
the average rate of concordance in chromosomal alterations
between paired samples was 81% (range, 65% to 100%), and
the pairs of lesions were morphologically similar. One pair
of samples had no agreement, having 2 and 20 alterations,
respectively. These findings indicate that situations classified
as “recurrence” in 17 cases were instances of persistent carci-
noma and that the eighteenth patient most likely had two in-
dependent foci of DCIS. The mean number of CGH changes
was lower in the initial lesions (8.8) than in recurrent DCIS
(10.7). The degree of concordance was not significantly
related to the time to recurrence.
It is generally accepted that most lower grade invasive
breast carcinomas evolve through a series of nonobligatory
abnormal stages of preneoplastic and neoplastic growth over
an uncertain period of time (most likely several years in du-
ration). These stages are recognized morphologically as hy-
perplasia, ADH, and DCIS, with the latter two representing
the penultimate and ultimate stages of preinvasive neoplas-
tic progression, respectively. Genetic analyses of matched
samples of ADH, DCIS, and invasive carcinoma have identi-
fied concordant allelic imbalances with similar frequencies,
indicating that ADH and DCIS are nonobligate precursors
to invasive carcinoma. ADH and low-grade DCIS are char-
acterized by recurrent losses of 16q and 17p, and gain of 1q.
The patterns of genetic aberrations in high-grade DCIS are
more heterogeneous, with only rare deletions of 16q. The
data, thus far, suggest that high-grade DCIS (those that are
ER negative and HER positive, express “basal” markers and
genomic aberrations) arise either
de novo
or from an as yet
unidentified precursor lesion—perhaps related to apocrine
lesions or to lesions like microglandular adenosis.
242
A gene signature of DCIS predictive of potential for ei-
ther recurrence or invasive carcinoma has, thus far, eluded
identification.
243
Livasy et al.
202
identified the “basal-like”
profile (i.e., ER negative, HER2 negative, EGFR positive, and
