Ductal Carcinoma
In Situ
333
Comedo-type (high-grade solid) DCIS was significantly
more frequent in the biennial (73.7%) than in the annual
(46.8%) screening group. Tumor size and nuclear grade were
inversely related to the mean sizes for low-, intermediate-,
and high-grade lesions determined to be 1.19, 1.85, and
2.82 cm, respectively. The frequency of microinvasion
tended to increase with longer intervals between examina-
tions, but the differences were not statistically significant.
Approximately 10% to 15% of DCIS are discovered as in-
cidental lesions in biopsies performed for other indications,
usually a palpable abnormality.
32,43,46
Radiologic findings
that lead to the detection of a small proportion of “inciden-
tal” DCIS are densities and asymmetric soft tissue changes,
sometimes with microcalcifications in the noncarcinoma-
tous abnormality. Calcifications alone are more likely to be
the mammographic indicator of DCIS in women younger
than 50 years, whereas coexistent soft tissue abnormalities
are evident more often in women older than 50, a distinc-
tion that probably results from variation in overall breast
density in these age groups rather than from intrinsic tumor
differences.
46
Relatively specific findings of DCIS on mammograms in-
clude microcalcifications of certain types and patterns, that
is, the calcifications may be pleomorphic, coarse, and fine
and are either clustered or linear in distribution.
47
Calcifica-
tions associated with DCIS are generally described as linear
“casts” or as granular on mammography (Fig. 11.1). Round
or oval, well-circumscribed calcifications are less common
in DCIS. Predominantly linear, granular, or mixed types
of calcifications occur with approximately equal frequency
in DCIS. Calcifications may be clustered, dispersed, or dis-
persed around clustered foci. Branching calcifications with
linear patterns that outline the distribution of one or more
ducts may consist of casts or granular particles. The type of
calcifications is not related to age at diagnosis or to the size
of the area involved mammographically.
46
The level of sus-
picion for DCIS is a function of the character and the num-
ber of calcifications. The majority of DCIS have five or more
calcifications.
46
On mammograms, linear, pleomorphic calcifications are
commonly seen in high-grade DCIS, and granular segmen-
tal calcifications are typical of lower grade lesions. Ducts
afflicted with high-grade DCIS harbor calcifications more
often than those with low-grade DCIS. In some cases of low-
grade DCIS, the majority of calcifications are in adjacent
benign glands. Thus, DCIS may be smaller, larger, or equal
to the extent of mammographic calcifications, and calcifica-
tions do not always “map-out” DCIS, particularly in lower
grade lesions. Despite such nuances, the mammographic
distribution of calcifications is commonly used as a guide to
the extent of DCIS or the dimensions of the involved area.
However, these measurements typically tend to underesti-
mate the size of the lesion compared with careful histologic
sampling.
49
When the extents of lesions were measured
mammographically and pathologically, discrepancies were
found more often between the interpretations for cases that
were predominantly cribriform or micropapillary than for
high-grade, solid DCIS. A discrepancy of more than 20 mm
was found in 44% of pure cribriform–micropapillary lesions,
The increased age-adjusted incidence of
in situ
breast
carcinoma in the United States coincides with a leveling off
in the overall age-adjusted incidence of invasive carcinoma
and of localized carcinoma, and a decline in the incidence of
invasive carcinoma classified as “regional.”
25
These changes
in incidence by stage have been accompanied by a signifi-
cant decline in age-adjusted breast carcinoma mortality.
25
The beneficial effects of mammography as a diagnostic or
screening modality, and of improved systemic therapy, are
reflected in these trends.
Although the incidence of DCIS has steeply escalated over
the last few decades, this rise has not been uniform across
various histologic types: low-grade DCIS has accounted for
the majority of the recent increase in incidence owing to en-
hanced radiologic detection, whereas the incidence of high-
grade DCIS has remained stable.
26
Risk Factors
Data on epidemiologic risk factors specific to DCIS are lim-
ited.
27,28
There appear to be some age-related differences in
associations, but overall the risk factors for DCIS and invasive
carcinoma appear to be similar.
27
The risk for both lesions
increases with age, an association that is stronger for inva-
sive carcinoma. Risk factors for incident DCIS include posi-
tive family history.
29
BRCA
(breast cancer [gene]) mutations
were found in 13% of women with DCIS diagnosed before
50 years of age.
30
In the largest analysis of DCIS patients in
non–Ashkenazi Jewish women, the prevalence of a
BRCA1/2
mutation was 5.9%.
31
The risk was significantly higher among
women younger than 50 years with a personal and family his-
tory of breast carcinoma than those 50 years or older.
Mammography and Calcifications
The great majority of currently diagnosed cases of DCIS are
nonpalpable and are detected by various radiologic tech-
niques. Mammography is a highly sensitive diagnostic pro-
cedure for detecting DCIS.
32
In 2002, it was estimated that
about 1 in every 1,300 screening mammograms resulted in
a diagnosis of DCIS.
33
Until recently, on initial screening,
8% to 43% of mammographically detected carcinomas were
intraductal.
34–40
Twenty-five percent to 30% of nonpalpable
carcinomas detected by mammography were intraductal
lesions.
37,41–43
In a series of nearly 20,000 patients, 30 of 70
carcinomas (43%) found in biopsies performed only for
clustered calcifications detected by mammography were
DCIS.
38
Mammographically detected calcifications were
found in 72% to 98% of DCIS.
44–47
The proportion of DCIS
was not substantially higher in subsequent mammography
screening, but some investigators have described a greater
frequency of small invasive tumors in later examinations.
34,39
The interval between screening examinations can influ-
ence the clinical characteristics of DCIS detected by mam-
mography.
48
The size of DCIS determined bymammographic
measurement was significantly smaller in women examined
annually (mean, 1.69 cm; range, 0.3 to 7.7 cm) than in those
examined on a biennial (mean, 2.27 cm; range, 0.4 to 10 cm)
or triennial (mean, 3.49 cm; range 0.6 to 10 cm) schedule.
