Although the term apocrine metaplasia certainly sounds sinister, it's not a medical condition that's life-threatening. An apocrine metaplasia refers to a lesion that occurs in the breast tissue that is, thankfully, benign. In fact, it's more common than most people realize, affecting far greater numbers of women than cancerous lesions ever do [source: Guray]. In fact, apocrine metaplasia has been discovered in about 90 percent of all women autopsied [source: Sanders].
The lesions, or cysts, are comprised of firm white fibrous tissue and may become tender at various times throughout the menstrual cycle. There are no clear-cut reasons why they occur, but it's thought an excess or shortage of estrogen or progesterone is to blame [source: Sanders]. Beginning at about age 20, women have increased odds of developing these cysts. By about age 40, the frequency drops off dramatically [source: Guray].
Apocrine metaplasia legions aren't typically associated with breast cancer or an increased risk of developing breast cancer. And, because they can be diagnosed with medical technology such as ultrasound, mammography or magnetic resonance imaging, there's also no need to surgically remove the benign cysts for further testing [source: Guray]. There is a school of thought, however, that apocrine metaplasia could progress into cancer, or at least reflect a propensity for the disease [source: Washington]. In most medical communities, this hypothesis is in the minority.
When it comes to extramammary Paget's disease, however, there is a direct link to cancer. We'll explain more about this condition on the next page.