**1. Introduction**

Cancer is considered to be the leading cause of death in developed countries and the second in developing countries. The burden of cancer is growing in economically developing countries due to population aging and adaption of cancer-associated lifestyle including smoking and Western diet. In 2008, it has been estimated that around 12.7 million cancer cases and 7.6 million cancer deaths have happened. Of these about 56% of the cases and 64% of the deaths have been recorded in the economically developing countries [1].

Breast cancer in female is the most common diagnosed cancers and the leading cause of cancer-related death in developed and developing countries. It accounted for 1.38 million

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

new cancer cases (23%) and 458,400 (14%) of the total cancer deaths in 2008 worldwide. Of these, about 50% of the cases of breast cancer and 60% of breast cancer deaths takes place in developing countries including Western and Northern Europe, North America, Australia and New Zealand [2]. In the United States, in 2008, the American Cancer Society (ACS) estimates that almost 182,500 women were diagnosed with breast cancer and during the year about 40,500 women lost their life due to breast cancer.

**Risk factor Category at risk Comparison category Relative** 

Current user for at least 5 years Never used 1.3

Ductal carcinoma in situ No abnormality detected 17.3

Hyperplasia with atypia No hyperplasia 5.3

Proliferation without atypia\* No abnormality detected 2.5 Proliferation with atypia No abnormality detected 4.9–5

Alcohol intake 2 drinks per day Non-drinker 1.2 Body mass index 80th percentile, age 55 or greater 20th percentile 1.2

Radiation exposure Repeated fluoroscopy No exposure 1.6 Radiation therapy for Hodgkin's

Early menarche Younger than 12 years Older than 15 years 1.3 Late menopause Older than 55 years Younger than 45 1.2–1.5 Age at first childbirth Nulliparous or first child after 30 First child before 20 1.7–1.9 Current age 65 or older Less than 65 5.8

Other histologic findings Lobular carcinoma in situ No abnormality detected 16.4

Breast biopsy Hyperplasia without atypia\* No hyperplasia 1.9

Hyperplasia with atypia and positive family history

Proliferation with atypia and positive family history

1st-degree relative with premenopausal breast cancer

Germline mutation Heterozygous for BRCA1, age < 40 Not heterozygous for

with postmenopausal breast cancer

2nd-degree relative with breast

Two 1st-degree relatives with breast

Heterozygous for BRCA1, age 60–69 Not heterozygous for

There is controversy over whether pathologic hyperplasia detected in breast biopsy samples is directly equivalent to

Family history 1st-degree relative 50 years or older

cancer

cancer

cytologic hyperplasia detected in samples obtained through FNA or nipple aspiration.

Past history of breast cancer Invasive breast carcinoma No history of invasive

disease

Hormone replacement therapy with estrogen and progesterone23

Cytology (fine-needle aspiration, nipple aspiration fluid)

**Table 1.** Risk factors for breast cancer.

\*

**risk**

105

6.8

11

1.8

3.3

1.5

3.6

200

15

No exposure 5.2

http://dx.doi.org/10.5772/intechopen.74679

breast carcinoma

Endocrine and Cell Surface Receptor Signaling in Breast Carcinogenesis

No hyperplasia, negative

No 1st- or 2nd-degree relative with breast cancer

No 1st- or 2nd-degree relative with breast cancer

No 1st- or 2nd-degree relative with breast cancer

No 1st- or 2nd-degree relative with breast cancer

BRCA1, age < 40

BRAC1, age 60–69

No abnormality detected 18.1

family history

The breast is made up of different types of tissues including fatty, lymphatic and connective tissue. A female breast is organized into 15–20 sections called lobes. Each of these lobes contains many smaller glandular structures called lobules which responsible for milk production. The lobes and lobules are connected through a network of tubes called ducts through which milk flows and reaches the nipple [3].

Majority of breast cancers arise from the cells in the duct or from milk-producing cells in the lobules. Increase in the incidence of breast cancer observed in epidemiological studies is as a result of breast cancer risk factors. About 20–30% of diagnosed cancer cases may be associated with these factors and their activity that lead to deregulation of the normal cellular processes into neoplastic transformation of breast cells [4]. However, about 75–80% of women with breast cancer have no identifiable risk factor [4]. Therefore, different system or model is required to be utilized to examine this cancer.
