Invasive breast carcinoma - IARC

Invasive breast carcinoma
I.O. Ellis
C.J. Cornelisse
S.J. Schnitt
A.J. Sasco
X. Sastre-Garau R. Kaaks
G. Bussolati P. Pisani
F.A. Tavassoli
D.E. Goldgar
V. Eusebi P. Devilee
J.L. Peterse M.J. Cleton-Jansen
K. Mukai A.L. Børresen-Dale
L. Tabár L. van’t Veer
J. Jacquemier A. Sapino
Definition
Invasive breast carcinoma is a group of
malignant epithelial tumours characterized
by invasion of adjacent tissues and
a marked tendency to metastasize to distant
sites. The vast majority of these tumours
are adenocarcinomas and are believed
to be derived from the mammary
p a renchymal epithelium, particularly cells
of the terminal duct lobular unit (TDLU).
B reast carcinomas exhibit a wide range
of morphological phenotypes and specific
histopathological types have part i c u l a r
p rognostic or clinical characteristics.
Epidemiology
Invasive breast cancer is the most common
carcinoma in women. It accounts for
22% of all female cancers, 26% in affluent
countries, which is more than twice
the occurrence of cancer in women at
any other site {2188}. The areas of high
risk are the affluent populations of North
America, Europe and Australia where 6%
of women develop invasive breast cancer
before age 75. The risk of breast cancer
is low in the less developed regions
of sub-Saharan Africa and Southern and
Eastern Asia, including Japan, where the
probability of developing breast cancer
by age 75 is one third that of rich countries.
Rates are intermediate elsewhere.
Japan is the only rich country that in year
2000 still showed low incidence rates.
The prognosis of the disease is very
good if detected at an early stage.
Significant improvements in survival have
been re c o rded in western countries
since the late 1970s {37,485}, but
advancements have been dramatic in
the 1990s due to the combined effect of
population screening and adjuvant hormonal
treatment. As a result, the increasing
mortality trend observed until the
1980s leveled off or declined in several
high risk countries e.g. the United States
of America (USA), the United Kingdom
and the Netherlands {3155}.
The risk of the disease had been increasing
until the early 1980s in both developed
and developing countries and continues
to increase in particular in the
developing countries {3068}. Thereafter,
in developed countries, the advent of
mammography and the previously mentioned
improvements in survival altered
both incidence and mortality; the latter
no longer appropriately reflect trends in
the underlying risk of the disease.
Breast cancer incidence, as with most
epithelial tumours, increases rapidly with
age. Figure 1.02 shows age-specific incidence
rates for three selected populations
re p resenting countries with low
(Japan), intermediate (Slovenia) and
high incidence rates (USA), just before
screening was implemented. The curves
show a characteristic shape, rising
steeply up to menopausal age and less
rapidly or not at all afterwards. The different
behaviour at older ages is due to a
cohort effect in the populations of Japan
and Slovenia experiencing an increase in
risk that affects mainly younger generations.
If current trends persist, these generations
will maintain their higher risk and
the age-specific curve will approach that
of Americans.
Around 1990, breast cancer incidence
varied 10-fold world wide, indicating
important differences in the distribution
of the underlying causes {2189}.
Geographical variations, time tre n d s ,
and studies of populations migrating
from low to high risk areas which show
that migrant populations approach the
risk of the host country in one or two generations
{174,1478,3266}, clearly suggest
an important role of environmental
factors in the aetiology of the disease.
Aetiology
The aetiology of breast cancer is multifactorial
and involves diet, reproductive
factors, and related hormonal imbalances.
From descriptive epidemiological
Fig. 1.01 Global incidence rates of breast cancer. Age-standardized rates (ASR) per 100,000 population and
year. From Globocan 2000 {846}.
Invasive breast cancer
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