Male breast cancer is similar to female breast cancer, and it develops in the same way in men as in women. Therefore, most of the information available on this site, including on development and progression, screening, diagnosis and treatment, applies to all affected people regardless of sex.

Although this cancer can develop in adults of any age, breast cancer usually strikes men between 60 and 70. The most common male breast cancer is ductal carcinoma, which forms in the mammary ducts.

Due to the lack of screening programs, men are often diagnosed at a later age and stage of the cancer than women are, resulting in a lower overall survival rate. However, the survival rates for men and women are similar when the same stages of the disease are compared. Over the years, as with female breast cancer, the survival rate has improved greatly.
Male breast cancer is under-researched. Clinical studies rarely include men, and the findings from studies with women are extrapolated to men. Studies are underway to better characterize male breast cancer and understand its biology to optimize treatment options. Male breast cancer is similar to female breast cancer, but it has several distinct characteristics due to hormonal differences.

Some of the symptoms of breast cancer men may notice are:

These signs may be related to an issue that is completely different than breast cancer and easily treatable. In fact, most breast-related health problems are not cancerous. If you are a man having one or more of these symptoms, you should nonetheless see a doctor. Only a medical examination by a healthcare professional can determine the problem and the appropriate treatment.

The main risk factors for male breast cancer are:

Note that these are risk factors—not certainties—of developing the disease. So you might have one or more of these factors and never develop breast cancer. However, other men might get breast cancer without having any of these risk factors.

Subtypes

The vast majority of human breast cancers express the ER and AR androgen hormone receptors.
The cancer cell mutations in men are not the same as those in women. For men, mutations are more often found in genes involved in DNA repair. Women have more mutations in the 16q, PI3KCA and TP53 genes.
The most commonly diagnosed type of male breast cancer is invasive ductal carcinoma since ductal carcinoma in situ is not palpable. Lobular carcinomas are rare (12%) because men generally do not have lobules (breast glands that make milk). Rarer breast cancers include papillary (34%) and mucinous (12%).

Treatments

In most cases, surgery is recommended. Total mastectomy is performed more often in men than lumpectomy. However, observational studies show that lumpectomy is as effective as mastectomy, and has the advantage of being more aesthetic and functional.
For men, studies suggest that radiation therapy is underutilized and that greater consideration of this treatment option would be beneficial. As with women, chemotherapy and HER2-targeted therapies should be used in men as neoadjuvant or adjuvant treatments.
Hormone therapy is often used, but the approach is different in men because of their different mechanisms of hormone production. Men generally receive Tamoxifen for 5 to 10 years, depending on their risk of recurrence and side effects.

The side effects of Tamoxifen for men include:

Aromatase inhibitors are less effective at lowering estrogen levels in men than in women. However, they can be taken with gonadotropin-releasing hormone analogues. More studies are needed to confirm the effectiveness of this combination.

Ongoing studies

Several studies are being conducted to improve male breast cancer treatments:

A growing number of breast cancer clinical studies are now recruiting men.
Some useful links:

Canadian Breast Cancer Network
Cancer Encyclopedia
Mount Sinai Hospital’s Marvelle Koffler Breast Centre
Directory of Centres de santé et de services sociaux (CSSS) in Quebec