Apocrine

An example of true apocrine glands is the mammary glands, responsible for secreting breast milk. Apocrine glands are also found in the anogenital region and axillae.

Apocrine secretion is less damaging to the gland than holocrine secretion (which destroys a cell) but more damaging than merocrine secretion (exocytosis).

Apocrine metaplasia

Apocrine metaplasia is a reversible transformation (metaplasia) of cells to an apocrine phenotype. It is common in the breast in the context of fibrocystic change. It is seen in women mostly over the age of 50 years. Metaplasia happens when there is an irritation to the breast (breast cyst). Apocrine-like cells form in a lining of developing microcysts, due to the pressure buildup within the lumen. The pressure build-up is caused by secretions. Such metaplasia represents an exception to the common rule of metaplasia's increasing the risk for developing cancer, in that apocrine metaplasia doesn't increase the possibility of developing breast cancer. Metaplastic apocrine cells belong to the category of oncocytes, which are a group characterized by abundant acidophilic, granular cytoplasm (from the Greek root onco-, which means mass, bulk).