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Innovation and clinical specialities: oncology
predict the risk of breast cancer, based on the above risk factors
identified in the American Caucasian population. The universal
applicability of these models can not, however be taken for
granted as the data on which they rely on were generated from
predominantly American Caucasian population and have not been
tested for African women 43,52,53
The most prominent statistical models are the Gail and the
Claus models. Gail and colleagues developed the most frequently
used model, which incorporates age at menarche, the number of
breast biopsies, age at first live birth, and the number of firstdegree
relatives with breast cancer. It predicts the cumulative risk
of breast cancer according to decade of life. To calculate breast
cancer risk with the Gail model, a woman's risk factors are
translated into an overall risk score by multiplying her relative risks
from several categories. This risk score is then compared to an
adjusted population risk of breast cancer to determine a woman’s
individual risk. A software programme incorporating the Gail
model is available from the National Cancer Institute at
http://bcra.nci.nih.gov/brc.
Claus and colleagues, using data from the Cancer and Steroid
Hormone Study, a case-control study of breast cancer, developed
the other frequently used risk-assessment model, which is based
on assumptions about the prevalence of high-penetrance breast
cancer susceptibility genes. Compared with the Gail model, the
Claus model incorporates more information about family history,
but excludes other risk factors. The Claus model provides
individual estimates of breast cancer risk according to decade of
life based on knowledge of first- and second-degree relatives with
breast cancer and their age at diagnosis. Risk factors that are
less-consistently associated with breast cancer (diet, use of oral
contraceptives, lactation), or are rare in the general population
(radiation exposure), are not included in either the Gail or Claus
risk-assessment models. 54
Pathology
Breast cancers are derived from the epithelial cells that line the
terminal duct lobular unit. Cancer cells that remain within the
basement membrane of the elements of the terminal duct lobular
unit and the draining duct are classified as in situ or non-invasive.
An invasive breast cancer is one in which there is dissemination of
cancer cells outside the basement membrane of the ducts and
lobules into the surrounding adjacent normal tissue.
Classification of Primary Breast Cancer
Noninvasive Epithelial Cancers
✚ Lobular Carcinoma in situ (LCIS).
✚ Ductal Carcinoma in situ (DCIS) or intraductal carcinoma:
Papillary, cribriform, solid and comedo types
Invasive Epithelial Cancers (percentage of total)
✚ Invasive lobular carcinoma (10-15).
✚ Invasive ductal carcinoma.
✚ Invasive ductal carcinoma, (NOS) Not Otherwise Specified
(50-70).
✚ Tubular carcinoma (2-3).
✚ Mucinous or colloid carcinoma (2-3).
✚ Medullary carcinoma (5).
✚ Invasive cribriform (1-3).
✚ Invasive papillary (1-2).
✚ Adenoid cystic carcinoma (1).
✚ Metaplastic carcinoma (1).
✚ Pagets disease (