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Male breast cancer accounts for less than 1% of all cancers in men and less than 1% of breast cancers.
This raises the question: Why do most breast cancers occur in women?
Two plausible explanations I can think of:
A male is less likely to get breast cancer for anatomical reasons (such as a smaller quantity of breast tissue, or breast tissue that is less susceptible to cancer),
Women have higher significantly levels of estrogen, which is linked to mutations that cause breast cancer (see Cavalieria et al. (2006)).
Although, I have no evidence to suggest that either of these is predominant factor.
$\begingroup$I agree that estrogen plays a very important role (among other hormonal cues). Another significant explanation that follows from your first example is the sheer quantity of female breasts to male breasts. While only some men have fatty breast tissue, all women do, and so the diagnoses are largely skewed by the anatomy. Something else to keep in mind is that women have breasts from puberty through the rest of their lives, while many men only develop them later in life.$\endgroup$
– user560
Sep 11, 2012 at 23:43
1
$\begingroup$There is another problem with breast cancer in men: Its usually not detected and searched for. Its probably happening more often than doctors think.$\endgroup$
First of all, there is an established link between breast cancer cell proliferation and concentration of estrogens and progesterone, which is logical, because normal breast cells divide in response to those hormones (e.g. puberty, pregnancy, even luteal phase of the menstrual cycle). Secondly, the incidence of breast cancer in women correlates with major changes in their hormonal profile - girls and elderly women (i.e. women with lower levels of sex hormones) don't get breast cancer.
Many factors, that influence the risk of developing breast cancer are in fact tightly connected to the hormones' levels. For example - early age of menarche (or, more importantly, first ovulation, because physical activity at young age disturbs ovulation AND is protective against breast cancer) and Hormone Replacement Therapy raise the risk, early age of first full-term pregnancy or any form of artificial menopause (such as preventive oophorectomy for women with mutations in BRCA1 or 2) reduce the risk.
The first table from the book chapter lists known risk and preventive factors. The review article explains the same ideas, but connects them to other types of cancer (e.g. ovarian cancer) and suggests mechanisms, which might be the cause of those risk changes.
$\begingroup$estrogen and prolactin are hormones that stimulate mammary development and growth of the breast tissue. They greatly enhance the chance of cancer since that tissues is proliferating at a great rate. Males do not typically experience these developmental phases.$\endgroup$
$\begingroup$This is a bad and poorly referenced answer. The age vs. cancer incidence for breast cancer follows essentially the same curve as every other adult cancer. There's no drop at menopause, and the highest incidence is in women over 70. There's a decrease in diagnosis in very elderly women, but this is seen in all adult cancers. Autopsy studies show us this isn't due to a magical protective age threshold, but different clinical choices due to age.$\endgroup$
the lobules in a woman's breast go through 4 stages:
Type 1: prepubescent & Type 2: pubescent
Type 3: reproductive & Type 4: lactation lobules²
The sooner a woman progresses to Type 3 and Type 4 lobules, the lower her risk of cancer. An interruption of the progression from Type 1 to Type 4 lobules (such as with a late-term miscarriage or induced abortion) increases the risk of cancer, as cancer generally arises in Type 1 and Type 2 lobules.³
$\begingroup$"or induced abortion" Isn't a(n adult) woman already at phase 3 (or what does it mean)? According to the source 3 non-adult women are in the category of increased risk. Women above 30 have increased risk of breast cancer probably due to the same reasons as people have other types of cancer, though.$\endgroup$
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