Breast cancer is by far the most common cancer in women.

The disease is characterized by a varied course, from rapidly growing tumors with early distant metastasis, to slow growing tumors which may stay in the breasts without metastasizing. 25-30% of these cases are agressive.

The majority of breast tumors are carcinomas. Sarcomatoid tumors are rare, but must be kept in mind as they are treated differently from other breast carcinomas. Breast cancer rarely occurs in men. In Norway, less than 20 cases are diagnosed per year. The treatment is similar as for women.

Incidence
Every 10^th to 11^th woman will develop breast cancer. In Norway in 2013, there were 3220 women who received this diagnosis. In comparison, the disease affected 1235 women in 1970. 36 men were diagnosed with breast cancer in 2013.Breast cancer involves first and foremost women over the age of 50. The average age at diagnosis is 59. The risk increases with age, but isolated cases also occur under 30 years of age.

For more information, see the Norwegian Breast Cancer Group.